[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Emacs-diffs] Changes to cl.texi
|
From: |
Glenn Morris |
|
Subject: |
[Emacs-diffs] Changes to cl.texi |
|
Date: |
Thu, 06 Sep 2007 04:59:02 +0000 |
CVSROOT: /sources/emacs
Module name: emacs
Changes by: Glenn Morris <gm> 07/09/06 04:59:02
Index: cl.texi
===================================================================
RCS file: cl.texi
diff -N cl.texi
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ cl.texi 6 Sep 2007 04:59:02 -0000 1.1
@@ -0,0 +1,5377 @@
+\input texinfo @c -*-texinfo-*-
address@hidden ../info/cl
address@hidden Common Lisp Extensions
+
address@hidden
+This file documents the GNU Emacs Common Lisp emulation package.
+
+Copyright @copyright{} 1993, 2001, 2002, 2003, 2004, 2005, 2006, 2007
+Free Software Foundation, Inc.
+
address@hidden
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with the Front-Cover texts being ``A GNU
+Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
+license is included in the section entitled ``GNU Free Documentation
+License'' in the Emacs manual.
+
+(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
+this GNU Manual, like GNU software. Copies published by the Free
+Software Foundation raise funds for GNU development.''
+
+This document is part of a collection distributed under the GNU Free
+Documentation License. If you want to distribute this document
+separately from the collection, you can do so by adding a copy of the
+license to the document, as described in section 6 of the license.
address@hidden quotation
address@hidden copying
+
address@hidden Emacs
address@hidden
+* CL: (cl). Partial Common Lisp support for Emacs Lisp.
address@hidden direntry
+
address@hidden
+
address@hidden
address@hidden 6
address@hidden @titlefont{Common Lisp Extensions}
address@hidden 4
address@hidden For GNU Emacs Lisp
address@hidden 1
address@hidden Version 2.02
address@hidden 5
address@hidden Dave Gillespie
address@hidden daveg@@synaptics.com
address@hidden
address@hidden 0pt plus 1filll
address@hidden
address@hidden titlepage
+
address@hidden Top, Overview, (dir), (dir)
address@hidden Introduction
+
address@hidden
+This document describes a set of Emacs Lisp facilities borrowed from
+Common Lisp. All the facilities are described here in detail. While
+this document does not assume any prior knowledge of Common Lisp, it
+does assume a basic familiarity with Emacs Lisp.
+
address@hidden
+* Overview:: Installation, usage, etc.
+* Program Structure:: Arglists, `eval-when', `defalias'
+* Predicates:: `typep', `eql', and `equalp'
+* Control Structure:: `setf', `do', `loop', etc.
+* Macros:: Destructuring, `define-compiler-macro'
+* Declarations:: `proclaim', `declare', etc.
+* Symbols:: Property lists, `gensym'
+* Numbers:: Predicates, functions, random numbers
+* Sequences:: Mapping, functions, searching, sorting
+* Lists:: `cadr', `sublis', `member*', `assoc*', etc.
+* Structures:: `defstruct'
+* Assertions:: `check-type', `assert', `ignore-errors'.
+
+* Efficiency Concerns:: Hints and techniques
+* Common Lisp Compatibility:: All known differences with Steele
+* Old CL Compatibility:: All known differences with old cl.el
+* Porting Common Lisp:: Hints for porting Common Lisp code
+
+* GNU Free Documentation License:: The license for this documentation.
+* Function Index::
+* Variable Index::
address@hidden menu
+
address@hidden Overview, Program Structure, Top, Top
address@hidden
address@hidden Overview
address@hidden ifnottex
+
address@hidden
+Common Lisp is a huge language, and Common Lisp systems tend to be
+massive and extremely complex. Emacs Lisp, by contrast, is rather
+minimalist in the choice of Lisp features it offers the programmer.
+As Emacs Lisp programmers have grown in number, and the applications
+they write have grown more ambitious, it has become clear that Emacs
+Lisp could benefit from many of the conveniences of Common Lisp.
+
+The @dfn{CL} package adds a number of Common Lisp functions and
+control structures to Emacs Lisp. While not a 100% complete
+implementation of Common Lisp, @dfn{CL} adds enough functionality
+to make Emacs Lisp programming significantly more convenient.
+
address@hidden note:} the @dfn{CL} functions are not standard parts of
+the Emacs Lisp name space, so it is legitimate for users to define
+them with other, conflicting meanings. To avoid conflicting with
+those user activities, we have a policy that packages installed in
+Emacs must not load @dfn{CL} at run time. (It is ok for them to load
address@hidden at compile time only, with @code{eval-when-compile}, and use
+the macros it provides.) If you are writing packages that you plan to
+distribute and invite widespread use for, you might want to observe
+the same rule.
+
+Some Common Lisp features have been omitted from this package
+for various reasons:
+
address@hidden @bullet
address@hidden
+Some features are too complex or bulky relative to their benefit
+to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
+examples of this group.
+
address@hidden
+Other features cannot be implemented without modification to the
+Emacs Lisp interpreter itself, such as multiple return values,
+lexical scoping, case-insensitive symbols, and complex numbers.
+The @dfn{CL} package generally makes no attempt to emulate these
+features.
+
address@hidden
+Some features conflict with existing things in Emacs Lisp. For
+example, Emacs' @code{assoc} function is incompatible with the
+Common Lisp @code{assoc}. In such cases, this package usually
+adds the suffix @samp{*} to the function name of the Common
+Lisp version of the function (e.g., @code{assoc*}).
address@hidden itemize
+
+The package described here was written by Dave Gillespie,
address@hidden@@synaptics.com}. It is a total rewrite of the original
+1986 @file{cl.el} package by Cesar Quiroz. Most features of the
+Quiroz package have been retained; any incompatibilities are
+noted in the descriptions below. Care has been taken in this
+version to ensure that each function is defined efficiently,
+concisely, and with minimal impact on the rest of the Emacs
+environment.
+
address@hidden
+* Usage:: How to use the CL package
+* Organization:: The package's five component files
+* Installation:: Compiling and installing CL
+* Naming Conventions:: Notes on CL function names
address@hidden menu
+
address@hidden Usage, Organization, Overview, Overview
address@hidden Usage
+
address@hidden
+Lisp code that uses features from the @dfn{CL} package should
+include at the beginning:
+
address@hidden
+(require 'cl)
address@hidden example
+
address@hidden
+If you want to ensure that the new (Gillespie) version of @dfn{CL}
+is the one that is present, add an additional @code{(require 'cl-19)}
+call:
+
address@hidden
+(require 'cl)
+(require 'cl-19)
address@hidden example
+
address@hidden
+The second call will fail (with address@hidden not found'') if
+the old @file{cl.el} package was in use.
+
+It is safe to arrange to load @dfn{CL} at all times, e.g.,
+in your @file{.emacs} file. But it's a good idea, for portability,
+to @code{(require 'cl)} in your code even if you do this.
+
address@hidden Organization, Installation, Usage, Overview
address@hidden Organization
+
address@hidden
+The Common Lisp package is organized into four files:
+
address@hidden @file
address@hidden cl.el
+This is the ``main'' file, which contains basic functions
+and information about the package. This file is relatively
+compact---about 700 lines.
+
address@hidden cl-extra.el
+This file contains the larger, more complex or unusual functions.
+It is kept separate so that packages which only want to use Common
+Lisp fundamentals like the @code{cadr} function won't need to pay
+the overhead of loading the more advanced functions.
+
address@hidden cl-seq.el
+This file contains most of the advanced functions for operating
+on sequences or lists, such as @code{delete-if} and @code{assoc*}.
+
address@hidden cl-macs.el
+This file contains the features of the packages which are macros
+instead of functions. Macros expand when the caller is compiled,
+not when it is run, so the macros generally only need to be
+present when the byte-compiler is running (or when the macros are
+used in uncompiled code such as a @file{.emacs} file). Most of
+the macros of this package are isolated in @file{cl-macs.el} so
+that they won't take up memory unless you are compiling.
address@hidden table
+
+The file @file{cl.el} includes all necessary @code{autoload}
+commands for the functions and macros in the other three files.
+All you have to do is @code{(require 'cl)}, and @file{cl.el}
+will take care of pulling in the other files when they are
+needed.
+
+There is another file, @file{cl-compat.el}, which defines some
+routines from the older @file{cl.el} package that are no longer
+present in the new package. This includes internal routines
+like @code{setelt} and @code{zip-lists}, deprecated features
+like @code{defkeyword}, and an emulation of the old-style
+multiple-values feature. @xref{Old CL Compatibility}.
+
address@hidden Installation, Naming Conventions, Organization, Overview
address@hidden Installation
+
address@hidden
+Installation of the @dfn{CL} package is simple: Just put the
+byte-compiled files @file{cl.elc}, @file{cl-extra.elc},
address@hidden, @file{cl-macs.elc}, and @file{cl-compat.elc}
+into a directory on your @code{load-path}.
+
+There are no special requirements to compile this package:
+The files do not have to be loaded before they are compiled,
+nor do they need to be compiled in any particular order.
+
+You may choose to put the files into your main @file{lisp/}
+directory, replacing the original @file{cl.el} file there. Or,
+you could put them into a directory that comes before @file{lisp/}
+on your @code{load-path} so that the old @file{cl.el} is
+effectively hidden.
+
+Also, format the @file{cl.texinfo} file and put the resulting
+Info files in the @file{info/} directory or another suitable place.
+
+You may instead wish to leave this package's components all in
+their own directory, and then add this directory to your
address@hidden and @code{Info-directory-list}.
+Add the directory to the front of the list so the old @dfn{CL}
+package and its documentation are hidden.
+
address@hidden Naming Conventions, , Installation, Overview
address@hidden Naming Conventions
+
address@hidden
+Except where noted, all functions defined by this package have the
+same names and calling conventions as their Common Lisp counterparts.
+
+Following is a complete list of functions whose names were changed
+from Common Lisp, usually to avoid conflicts with Emacs. In each
+case, a @samp{*} has been appended to the Common Lisp name to obtain
+the Emacs name:
+
address@hidden
+defun* defsubst* defmacro* function*
+member* assoc* rassoc* get*
+remove* delete* mapcar* sort*
+floor* ceiling* truncate* round*
+mod* rem* random*
address@hidden example
+
+Internal function and variable names in the package are prefixed
+by @code{cl-}. Here is a complete list of functions @emph{not}
+prefixed by @code{cl-} which were not taken from Common Lisp:
+
address@hidden
+floatp-safe lexical-let lexical-let*
+callf callf2 letf letf*
+defsubst*
address@hidden example
+
+The following simple functions and macros are defined in @file{cl.el};
+they do not cause other components like @file{cl-extra} to be loaded.
+
address@hidden
+eql floatp-safe endp
+evenp oddp plusp minusp
+caaar .. cddddr
+list* ldiff rest first .. tenth
+copy-list subst mapcar* [2]
+adjoin [3] acons pairlis pop [4]
+push [4] pushnew [3,4] incf [4] decf [4]
+proclaim declaim
address@hidden example
+
address@hidden
+[2] Only for one sequence argument or two list arguments.
+
address@hidden
+[3] Only if @code{:test} is @code{eq}, @code{equal}, or unspecified,
+and @code{:key} is not used.
+
address@hidden
+[4] Only when @var{place} is a plain variable name.
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Program Structure, Predicates, Overview, Top
address@hidden Program Structure
+
address@hidden
+This section describes features of the @dfn{CL} package which have to
+do with programs as a whole: advanced argument lists for functions,
+and the @code{eval-when} construct.
+
address@hidden
+* Argument Lists:: `&key', `&aux', `defun*', `defmacro*'.
+* Time of Evaluation:: The `eval-when' construct.
address@hidden menu
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Argument Lists, Time of Evaluation, Program Structure, Program
Structure
address@hidden Argument Lists
+
address@hidden
+Emacs Lisp's notation for argument lists of functions is a subset of
+the Common Lisp notation. As well as the familiar @code{&optional}
+and @code{&rest} markers, Common Lisp allows you to specify default
+values for optional arguments, and it provides the additional markers
address@hidden&key} and @code{&aux}.
+
+Since argument parsing is built-in to Emacs, there is no way for
+this package to implement Common Lisp argument lists seamlessly.
+Instead, this package defines alternates for several Lisp forms
+which you must use if you need Common Lisp argument lists.
+
address@hidden defun* name arglist body...
+This form is identical to the regular @code{defun} form, except
+that @var{arglist} is allowed to be a full Common Lisp argument
+list. Also, the function body is enclosed in an implicit block
+called @var{name}; @pxref{Blocks and Exits}.
address@hidden defspec
+
address@hidden defsubst* name arglist body...
+This is just like @code{defun*}, except that the function that
+is defined is automatically proclaimed @code{inline}, i.e.,
+calls to it may be expanded into in-line code by the byte compiler.
+This is analogous to the @code{defsubst} form;
address@hidden uses a different method (compiler macros) which
+works in all version of Emacs, and also generates somewhat more
+efficient inline expansions. In particular, @code{defsubst*}
+arranges for the processing of keyword arguments, default values,
+etc., to be done at compile-time whenever possible.
address@hidden defspec
+
address@hidden defmacro* name arglist body...
+This is identical to the regular @code{defmacro} form,
+except that @var{arglist} is allowed to be a full Common Lisp
+argument list. The @code{&environment} keyword is supported as
+described in Steele. The @code{&whole} keyword is supported only
+within destructured lists (see below); top-level @code{&whole}
+cannot be implemented with the current Emacs Lisp interpreter.
+The macro expander body is enclosed in an implicit block called
address@hidden
address@hidden defspec
+
address@hidden function* symbol-or-lambda
+This is identical to the regular @code{function} form,
+except that if the argument is a @code{lambda} form then that
+form may use a full Common Lisp argument list.
address@hidden defspec
+
+Also, all forms (such as @code{defsetf} and @code{flet}) defined
+in this package that include @var{arglist}s in their syntax allow
+full Common Lisp argument lists.
+
+Note that it is @emph{not} necessary to use @code{defun*} in
+order to have access to most @dfn{CL} features in your function.
+These features are always present; @code{defun*}'s only
+difference from @code{defun} is its more flexible argument
+lists and its implicit block.
+
+The full form of a Common Lisp argument list is
+
address@hidden
+(@var{var}...
+ &optional (@var{var} @var{initform} @var{svar})...
+ &rest @var{var}
+ &key ((@var{keyword} @var{var}) @var{initform} @var{svar})...
+ &aux (@var{var} @var{initform})...)
address@hidden example
+
+Each of the five argument list sections is optional. The @var{svar},
address@hidden, and @var{keyword} parts are optional; if they are
+omitted, then @samp{(@var{var})} may be written simply @address@hidden
+
+The first section consists of zero or more @dfn{required} arguments.
+These arguments must always be specified in a call to the function;
+there is no difference between Emacs Lisp and Common Lisp as far as
+required arguments are concerned.
+
+The second section consists of @dfn{optional} arguments. These
+arguments may be specified in the function call; if they are not,
address@hidden specifies the default value used for the argument.
+(No @var{initform} means to use @code{nil} as the default.) The
address@hidden is evaluated with the bindings for the preceding
+arguments already established; @code{(a &optional (b (1+ a)))}
+matches one or two arguments, with the second argument defaulting
+to one plus the first argument. If the @var{svar} is specified,
+it is an auxiliary variable which is bound to @code{t} if the optional
+argument was specified, or to @code{nil} if the argument was omitted.
+If you don't use an @var{svar}, then there will be no way for your
+function to tell whether it was called with no argument, or with
+the default value passed explicitly as an argument.
+
+The third section consists of a single @dfn{rest} argument. If
+more arguments were passed to the function than are accounted for
+by the required and optional arguments, those extra arguments are
+collected into a list and bound to the ``rest'' argument variable.
+Common Lisp's @code{&rest} is equivalent to that of Emacs Lisp.
+Common Lisp accepts @code{&body} as a synonym for @code{&rest} in
+macro contexts; this package accepts it all the time.
+
+The fourth section consists of @dfn{keyword} arguments. These
+are optional arguments which are specified by name rather than
+positionally in the argument list. For example,
+
address@hidden
+(defun* foo (a &optional b &key c d (e 17)))
address@hidden example
+
address@hidden
+defines a function which may be called with one, two, or more
+arguments. The first two arguments are bound to @code{a} and
address@hidden in the usual way. The remaining arguments must be
+pairs of the form @code{:c}, @code{:d}, or @code{:e} followed
+by the value to be bound to the corresponding argument variable.
+(Symbols whose names begin with a colon are called @dfn{keywords},
+and they are self-quoting in the same way as @code{nil} and
address@hidden)
+
+For example, the call @code{(foo 1 2 :d 3 :c 4)} sets the five
+arguments to 1, 2, 4, 3, and 17, respectively. If the same keyword
+appears more than once in the function call, the first occurrence
+takes precedence over the later ones. Note that it is not possible
+to specify keyword arguments without specifying the optional
+argument @code{b} as well, since @code{(foo 1 :c 2)} would bind
address@hidden to the keyword @code{:c}, then signal an error because
address@hidden is not a valid keyword.
+
+If a @var{keyword} symbol is explicitly specified in the argument
+list as shown in the above diagram, then that keyword will be
+used instead of just the variable name prefixed with a colon.
+You can specify a @var{keyword} symbol which does not begin with
+a colon at all, but such symbols will not be self-quoting; you
+will have to quote them explicitly with an apostrophe in the
+function call.
+
+Ordinarily it is an error to pass an unrecognized keyword to
+a function, e.g., @code{(foo 1 2 :c 3 :goober 4)}. You can ask
+Lisp to ignore unrecognized keywords, either by adding the
+marker @code{&allow-other-keys} after the keyword section
+of the argument list, or by specifying an @code{:allow-other-keys}
+argument in the call whose value is address@hidden If the
+function uses both @code{&rest} and @code{&key} at the same time,
+the ``rest'' argument is bound to the keyword list as it appears
+in the call. For example:
+
address@hidden
+(defun* find-thing (thing &rest rest &key need &allow-other-keys)
+ (or (apply 'member* thing thing-list :allow-other-keys t rest)
+ (if need (error "Thing not found"))))
address@hidden smallexample
+
address@hidden
+This function takes a @code{:need} keyword argument, but also
+accepts other keyword arguments which are passed on to the
address@hidden function. @code{allow-other-keys} is used to
+keep both @code{find-thing} and @code{member*} from complaining
+about each others' keywords in the arguments.
+
+The fifth section of the argument list consists of @dfn{auxiliary
+variables}. These are not really arguments at all, but simply
+variables which are bound to @code{nil} or to the specified
address@hidden during execution of the function. There is no
+difference between the following two functions, except for a
+matter of stylistic taste:
+
address@hidden
+(defun* foo (a b &aux (c (+ a b)) d)
+ @var{body})
+
+(defun* foo (a b)
+ (let ((c (+ a b)) d)
+ @var{body}))
address@hidden example
+
+Argument lists support @dfn{destructuring}. In Common Lisp,
+destructuring is only allowed with @code{defmacro}; this package
+allows it with @code{defun*} and other argument lists as well.
+In destructuring, any argument variable (@var{var} in the above
+diagram) can be replaced by a list of variables, or more generally,
+a recursive argument list. The corresponding argument value must
+be a list whose elements match this recursive argument list.
+For example:
+
address@hidden
+(defmacro* dolist ((var listform &optional resultform)
+ &rest body)
+ ...)
address@hidden example
+
+This says that the first argument of @code{dolist} must be a list
+of two or three items; if there are other arguments as well as this
+list, they are stored in @code{body}. All features allowed in
+regular argument lists are allowed in these recursive argument lists.
+In addition, the clause @samp{&whole @var{var}} is allowed at the
+front of a recursive argument list. It binds @var{var} to the
+whole list being matched; thus @code{(&whole all a b)} matches
+a list of two things, with @code{a} bound to the first thing,
address@hidden bound to the second thing, and @code{all} bound to the
+list itself. (Common Lisp allows @code{&whole} in top-level
address@hidden argument lists as well, but Emacs Lisp does not
+support this usage.)
+
+One last feature of destructuring is that the argument list may be
+dotted, so that the argument list @code{(a b . c)} is functionally
+equivalent to @code{(a b &rest c)}.
+
+If the optimization quality @code{safety} is set to 0
+(@pxref{Declarations}), error checking for wrong number of
+arguments and invalid keyword arguments is disabled. By default,
+argument lists are rigorously checked.
+
address@hidden Time of Evaluation, , Argument Lists, Program Structure
address@hidden Time of Evaluation
+
address@hidden
+Normally, the byte-compiler does not actually execute the forms in
+a file it compiles. For example, if a file contains @code{(setq foo t)},
+the act of compiling it will not actually set @code{foo} to @code{t}.
+This is true even if the @code{setq} was a top-level form (i.e., not
+enclosed in a @code{defun} or other form). Sometimes, though, you
+would like to have certain top-level forms evaluated at compile-time.
+For example, the compiler effectively evaluates @code{defmacro} forms
+at compile-time so that later parts of the file can refer to the
+macros that are defined.
+
address@hidden eval-when (situations...) forms...
+This form controls when the body @var{forms} are evaluated.
+The @var{situations} list may contain any set of the symbols
address@hidden, @code{load}, and @code{eval} (or their long-winded
+ANSI equivalents, @code{:compile-toplevel}, @code{:load-toplevel},
+and @code{:execute}).
+
+The @code{eval-when} form is handled differently depending on
+whether or not it is being compiled as a top-level form.
+Specifically, it gets special treatment if it is being compiled
+by a command such as @code{byte-compile-file} which compiles files
+or buffers of code, and it appears either literally at the
+top level of the file or inside a top-level @code{progn}.
+
+For compiled top-level @code{eval-when}s, the body @var{forms} are
+executed at compile-time if @code{compile} is in the @var{situations}
+list, and the @var{forms} are written out to the file (to be executed
+at load-time) if @code{load} is in the @var{situations} list.
+
+For non-compiled-top-level forms, only the @code{eval} situation is
+relevant. (This includes forms executed by the interpreter, forms
+compiled with @code{byte-compile} rather than @code{byte-compile-file},
+and non-top-level forms.) The @code{eval-when} acts like a
address@hidden if @code{eval} is specified, and like @code{nil}
+(ignoring the body @var{forms}) if not.
+
+The rules become more subtle when @code{eval-when}s are nested;
+consult Steele (second edition) for the gruesome details (and
+some gruesome examples).
+
+Some simple examples:
+
address@hidden
+;; Top-level forms in foo.el:
+(eval-when (compile) (setq foo1 'bar))
+(eval-when (load) (setq foo2 'bar))
+(eval-when (compile load) (setq foo3 'bar))
+(eval-when (eval) (setq foo4 'bar))
+(eval-when (eval compile) (setq foo5 'bar))
+(eval-when (eval load) (setq foo6 'bar))
+(eval-when (eval compile load) (setq foo7 'bar))
address@hidden example
+
+When @file{foo.el} is compiled, these variables will be set during
+the compilation itself:
+
address@hidden
+foo1 foo3 foo5 foo7 ; `compile'
address@hidden example
+
+When @file{foo.elc} is loaded, these variables will be set:
+
address@hidden
+foo2 foo3 foo6 foo7 ; `load'
address@hidden example
+
+And if @file{foo.el} is loaded uncompiled, these variables will
+be set:
+
address@hidden
+foo4 foo5 foo6 foo7 ; `eval'
address@hidden example
+
+If these seven @code{eval-when}s had been, say, inside a @code{defun},
+then the first three would have been equivalent to @code{nil} and the
+last four would have been equivalent to the corresponding @code{setq}s.
+
+Note that @code{(eval-when (load eval) @dots{})} is equivalent
+to @code{(progn @dots{})} in all contexts. The compiler treats
+certain top-level forms, like @code{defmacro} (sort-of) and
address@hidden, as if they were wrapped in @code{(eval-when
+(compile load eval) @dots{})}.
address@hidden defspec
+
+Emacs includes two special forms related to @code{eval-when}.
+One of these, @code{eval-when-compile}, is not quite equivalent to
+any @code{eval-when} construct and is described below.
+
+The other form, @code{(eval-and-compile @dots{})}, is exactly
+equivalent to @samp{(eval-when (compile load eval) @dots{})} and
+so is not itself defined by this package.
+
address@hidden eval-when-compile forms...
+The @var{forms} are evaluated at compile-time; at execution time,
+this form acts like a quoted constant of the resulting value. Used
+at top-level, @code{eval-when-compile} is just like @samp{eval-when
+(compile eval)}. In other contexts, @code{eval-when-compile}
+allows code to be evaluated once at compile-time for efficiency
+or other reasons.
+
+This form is similar to the @samp{#.} syntax of true Common Lisp.
address@hidden defspec
+
address@hidden load-time-value form
+The @var{form} is evaluated at load-time; at execution time,
+this form acts like a quoted constant of the resulting value.
+
+Early Common Lisp had a @samp{#,} syntax that was similar to
+this, but ANSI Common Lisp replaced it with @code{load-time-value}
+and gave it more well-defined semantics.
+
+In a compiled file, @code{load-time-value} arranges for @var{form}
+to be evaluated when the @file{.elc} file is loaded and then used
+as if it were a quoted constant. In code compiled by
address@hidden rather than @code{byte-compile-file}, the
+effect is identical to @code{eval-when-compile}. In uncompiled
+code, both @code{eval-when-compile} and @code{load-time-value}
+act exactly like @code{progn}.
+
address@hidden
+(defun report ()
+ (insert "This function was executed on: "
+ (current-time-string)
+ ", compiled on: "
+ (eval-when-compile (current-time-string))
+ ;; or '#.(current-time-string) in real Common Lisp
+ ", and loaded on: "
+ (load-time-value (current-time-string))))
address@hidden example
+
address@hidden
+Byte-compiled, the above defun will result in the following code
+(or its compiled equivalent, of course) in the @file{.elc} file:
+
address@hidden
+(setq --temp-- (current-time-string))
+(defun report ()
+ (insert "This function was executed on: "
+ (current-time-string)
+ ", compiled on: "
+ '"Wed Jun 23 18:33:43 1993"
+ ", and loaded on: "
+ --temp--))
address@hidden example
address@hidden defspec
+
address@hidden Predicates, Control Structure, Program Structure, Top
address@hidden Predicates
+
address@hidden
+This section describes functions for testing whether various
+facts are true or false.
+
address@hidden
+* Type Predicates:: `typep', `deftype', and `coerce'
+* Equality Predicates:: `eql' and `equalp'
address@hidden menu
+
address@hidden Type Predicates, Equality Predicates, Predicates, Predicates
address@hidden Type Predicates
+
address@hidden
+The @dfn{CL} package defines a version of the Common Lisp @code{typep}
+predicate.
+
address@hidden typep object type
+Check if @var{object} is of type @var{type}, where @var{type} is a
+(quoted) type name of the sort used by Common Lisp. For example,
address@hidden(typep foo 'integer)} is equivalent to @code{(integerp foo)}.
address@hidden defun
+
+The @var{type} argument to the above function is either a symbol
+or a list beginning with a symbol.
+
address@hidden @bullet
address@hidden
+If the type name is a symbol, Emacs appends @samp{-p} to the
+symbol name to form the name of a predicate function for testing
+the type. (Built-in predicates whose names end in @samp{p} rather
+than @samp{-p} are used when appropriate.)
+
address@hidden
+The type symbol @code{t} stands for the union of all types.
address@hidden(typep @var{object} t)} is always true. Likewise, the
+type symbol @code{nil} stands for nothing at all, and
address@hidden(typep @var{object} nil)} is always false.
+
address@hidden
+The type symbol @code{null} represents the symbol @code{nil}.
+Thus @code{(typep @var{object} 'null)} is equivalent to
address@hidden(null @var{object})}.
+
address@hidden
+The type symbol @code{atom} represents all objects that are not cons
+cells. Thus @code{(typep @var{object} 'atom)} is equivalent to
address@hidden(atom @var{object})}.
+
address@hidden
+The type symbol @code{real} is a synonym for @code{number}, and
address@hidden is a synonym for @code{integer}.
+
address@hidden
+The type symbols @code{character} and @code{string-char} match
+integers in the range from 0 to 255.
+
address@hidden
+The type symbol @code{float} uses the @code{floatp-safe} predicate
+defined by this package rather than @code{floatp}, so it will work
+correctly even in Emacs versions without floating-point support.
+
address@hidden
+The type list @code{(integer @var{low} @var{high})} represents all
+integers between @var{low} and @var{high}, inclusive. Either bound
+may be a list of a single integer to specify an exclusive limit,
+or a @code{*} to specify no limit. The type @code{(integer * *)}
+is thus equivalent to @code{integer}.
+
address@hidden
+Likewise, lists beginning with @code{float}, @code{real}, or
address@hidden represent numbers of that type falling in a particular
+range.
+
address@hidden
+Lists beginning with @code{and}, @code{or}, and @code{not} form
+combinations of types. For example, @code{(or integer (float 0 *))}
+represents all objects that are integers or non-negative floats.
+
address@hidden
+Lists beginning with @code{member} or @code{member*} represent
+objects @code{eql} to any of the following values. For example,
address@hidden(member 1 2 3 4)} is equivalent to @code{(integer 1 4)},
+and @code{(member nil)} is equivalent to @code{null}.
+
address@hidden
+Lists of the form @code{(satisfies @var{predicate})} represent
+all objects for which @var{predicate} returns true when called
+with that object as an argument.
address@hidden itemize
+
+The following function and macro (not technically predicates) are
+related to @code{typep}.
+
address@hidden coerce object type
+This function attempts to convert @var{object} to the specified
address@hidden If @var{object} is already of that type as determined by
address@hidden, it is simply returned. Otherwise, certain types of
+conversions will be made: If @var{type} is any sequence type
+(@code{string}, @code{list}, etc.) then @var{object} will be
+converted to that type if possible. If @var{type} is
address@hidden, then strings of length one and symbols with
+one-character names can be coerced. If @var{type} is @code{float},
+then integers can be coerced in versions of Emacs that support
+floats. In all other circumstances, @code{coerce} signals an
+error.
address@hidden defun
+
address@hidden deftype name arglist forms...
+This macro defines a new type called @var{name}. It is similar
+to @code{defmacro} in many ways; when @var{name} is encountered
+as a type name, the body @var{forms} are evaluated and should
+return a type specifier that is equivalent to the type. The
address@hidden is a Common Lisp argument list of the sort accepted
+by @code{defmacro*}. The type specifier @samp{(@var{name} @var{args}...)}
+is expanded by calling the expander with those arguments; the type
+symbol @address@hidden is expanded by calling the expander with
+no arguments. The @var{arglist} is processed the same as for
address@hidden except that optional arguments without explicit
+defaults use @code{*} instead of @code{nil} as the ``default''
+default. Some examples:
+
address@hidden
+(deftype null () '(satisfies null)) ; predefined
+(deftype list () '(or null cons)) ; predefined
+(deftype unsigned-byte (&optional bits)
+ (list 'integer 0 (if (eq bits '*) bits (1- (lsh 1 bits)))))
+(unsigned-byte 8) @equiv{} (integer 0 255)
+(unsigned-byte) @equiv{} (integer 0 *)
+unsigned-byte @equiv{} (integer 0 *)
address@hidden example
+
address@hidden
+The last example shows how the Common Lisp @code{unsigned-byte}
+type specifier could be implemented if desired; this package does
+not implement @code{unsigned-byte} by default.
address@hidden defspec
+
+The @code{typecase} and @code{check-type} macros also use type
+names. @xref{Conditionals}. @xref{Assertions}. The @code{map},
address@hidden, and @code{merge} functions take type-name
+arguments to specify the type of sequence to return. @xref{Sequences}.
+
address@hidden Equality Predicates, , Type Predicates, Predicates
address@hidden Equality Predicates
+
address@hidden
+This package defines two Common Lisp predicates, @code{eql} and
address@hidden
+
address@hidden eql a b
+This function is almost the same as @code{eq}, except that if @var{a}
+and @var{b} are numbers of the same type, it compares them for numeric
+equality (as if by @code{equal} instead of @code{eq}). This makes a
+difference only for versions of Emacs that are compiled with
+floating-point support. Emacs floats are allocated
+objects just like cons cells, which means that @code{(eq 3.0 3.0)}
+will not necessarily be true---if the two @code{3.0}s were allocated
+separately, the pointers will be different even though the numbers are
+the same. But @code{(eql 3.0 3.0)} will always be true.
+
+The types of the arguments must match, so @code{(eql 3 3.0)} is
+still false.
+
+Note that Emacs integers are ``direct'' rather than allocated, which
+basically means @code{(eq 3 3)} will always be true. Thus @code{eq}
+and @code{eql} behave differently only if floating-point numbers are
+involved, and are indistinguishable on Emacs versions that don't
+support floats.
+
+There is a slight inconsistency with Common Lisp in the treatment of
+positive and negative zeros. Some machines, notably those with IEEE
+standard arithmetic, represent @code{+0} and @code{-0} as distinct
+values. Normally this doesn't matter because the standard specifies
+that @code{(= 0.0 -0.0)} should always be true, and this is indeed
+what Emacs Lisp and Common Lisp do. But the Common Lisp standard
+states that @code{(eql 0.0 -0.0)} and @code{(equal 0.0 -0.0)} should
+be false on IEEE-like machines; Emacs Lisp does not do this, and in
+fact the only known way to distinguish between the two zeros in Emacs
+Lisp is to @code{format} them and check for a minus sign.
address@hidden defun
+
address@hidden equalp a b
+This function is a more flexible version of @code{equal}. In
+particular, it compares strings case-insensitively, and it compares
+numbers without regard to type (so that @code{(equalp 3 3.0)} is
+true). Vectors and conses are compared recursively. All other
+objects are compared as if by @code{equal}.
+
+This function differs from Common Lisp @code{equalp} in several
+respects. First, Common Lisp's @code{equalp} also compares
address@hidden case-insensitively, which would be impractical
+in this package since Emacs does not distinguish between integers
+and characters. In keeping with the idea that strings are less
+vector-like in Emacs Lisp, this package's @code{equalp} also will
+not compare strings against vectors of integers.
address@hidden defun
+
+Also note that the Common Lisp functions @code{member} and @code{assoc}
+use @code{eql} to compare elements, whereas Emacs Lisp follows the
+MacLisp tradition and uses @code{equal} for these two functions.
+In Emacs, use @code{member*} and @code{assoc*} to get functions
+which use @code{eql} for comparisons.
+
address@hidden Control Structure, Macros, Predicates, Top
address@hidden Control Structure
+
address@hidden
+The features described in the following sections implement
+various advanced control structures, including the powerful
address@hidden facility and a number of looping and conditional
+constructs.
+
address@hidden
+* Assignment:: The `psetq' form
+* Generalized Variables:: `setf', `incf', `push', etc.
+* Variable Bindings:: `progv', `lexical-let', `flet', `macrolet'
+* Conditionals:: `case', `typecase'
+* Blocks and Exits:: `block', `return', `return-from'
+* Iteration:: `do', `dotimes', `dolist', `do-symbols'
+* Loop Facility:: The Common Lisp `loop' macro
+* Multiple Values:: `values', `multiple-value-bind', etc.
address@hidden menu
+
address@hidden Assignment, Generalized Variables, Control Structure, Control
Structure
address@hidden Assignment
+
address@hidden
+The @code{psetq} form is just like @code{setq}, except that multiple
+assignments are done in parallel rather than sequentially.
+
address@hidden psetq [symbol address@hidden
+This special form (actually a macro) is used to assign to several
+variables simultaneously. Given only one @var{symbol} and @var{form},
+it has the same effect as @code{setq}. Given several @var{symbol}
+and @var{form} pairs, it evaluates all the @var{form}s in advance
+and then stores the corresponding variables afterwards.
+
address@hidden
+(setq x 2 y 3)
+(setq x (+ x y) y (* x y))
+x
+ @result{} 5
+y ; @address@hidden was computed after @code{x} was set.}
+ @result{} 15
+(setq x 2 y 3)
+(psetq x (+ x y) y (* x y))
+x
+ @result{} 5
+y ; @address@hidden was computed before @code{x} was set.}
+ @result{} 6
address@hidden example
+
+The simplest use of @code{psetq} is @code{(psetq x y y x)}, which
+exchanges the values of two variables. (The @code{rotatef} form
+provides an even more convenient way to swap two variables;
address@hidden Macros}.)
+
address@hidden always returns @code{nil}.
address@hidden defspec
+
address@hidden Generalized Variables, Variable Bindings, Assignment, Control
Structure
address@hidden Generalized Variables
+
address@hidden
+A ``generalized variable'' or ``place form'' is one of the many places
+in Lisp memory where values can be stored. The simplest place form is
+a regular Lisp variable. But the cars and cdrs of lists, elements
+of arrays, properties of symbols, and many other locations are also
+places where Lisp values are stored.
+
+The @code{setf} form is like @code{setq}, except that it accepts
+arbitrary place forms on the left side rather than just
+symbols. For example, @code{(setf (car a) b)} sets the car of
address@hidden to @code{b}, doing the same operation as @code{(setcar a b)}
+but without having to remember two separate functions for setting
+and accessing every type of place.
+
+Generalized variables are analogous to ``lvalues'' in the C
+language, where @samp{x = a[i]} gets an element from an array
+and @samp{a[i] = x} stores an element using the same notation.
+Just as certain forms like @code{a[i]} can be lvalues in C, there
+is a set of forms that can be generalized variables in Lisp.
+
address@hidden
+* Basic Setf:: `setf' and place forms
+* Modify Macros:: `incf', `push', `rotatef', `letf', `callf', etc.
+* Customizing Setf:: `define-modify-macro', `defsetf', `define-setf-method'
address@hidden menu
+
address@hidden Basic Setf, Modify Macros, Generalized Variables, Generalized
Variables
address@hidden Basic Setf
+
address@hidden
+The @code{setf} macro is the most basic way to operate on generalized
+variables.
+
address@hidden setf [place address@hidden
+This macro evaluates @var{form} and stores it in @var{place}, which
+must be a valid generalized variable form. If there are several
address@hidden and @var{form} pairs, the assignments are done sequentially
+just as with @code{setq}. @code{setf} returns the value of the last
address@hidden
+
+The following Lisp forms will work as generalized variables, and
+so may appear in the @var{place} argument of @code{setf}:
+
address@hidden @bullet
address@hidden
+A symbol naming a variable. In other words, @code{(setf x y)} is
+exactly equivalent to @code{(setq x y)}, and @code{setq} itself is
+strictly speaking redundant now that @code{setf} exists. Many
+programmers continue to prefer @code{setq} for setting simple
+variables, though, purely for stylistic or historical reasons.
+The macro @code{(setf x y)} actually expands to @code{(setq x y)},
+so there is no performance penalty for using it in compiled code.
+
address@hidden
+A call to any of the following Lisp functions:
+
address@hidden
+car cdr caar .. cddddr
+nth rest first .. tenth
+aref elt nthcdr
+symbol-function symbol-value symbol-plist
+get get* getf
+gethash subseq
address@hidden smallexample
+
address@hidden
+Note that for @code{nthcdr} and @code{getf}, the list argument
+of the function must itself be a valid @var{place} form. For
+example, @code{(setf (nthcdr 0 foo) 7)} will set @code{foo} itself
+to 7. Note that @code{push} and @code{pop} on an @code{nthcdr}
+place can be used to insert or delete at any position in a list.
+The use of @code{nthcdr} as a @var{place} form is an extension
+to standard Common Lisp.
+
address@hidden
+The following Emacs-specific functions are also @code{setf}-able.
+
address@hidden
+buffer-file-name marker-position
+buffer-modified-p match-data
+buffer-name mouse-position
+buffer-string overlay-end
+buffer-substring overlay-get
+current-buffer overlay-start
+current-case-table point
+current-column point-marker
+current-global-map point-max
+current-input-mode point-min
+current-local-map process-buffer
+current-window-configuration process-filter
+default-file-modes process-sentinel
+default-value read-mouse-position
+documentation-property screen-height
+extent-data screen-menubar
+extent-end-position screen-width
+extent-start-position selected-window
+face-background selected-screen
+face-background-pixmap selected-frame
+face-font standard-case-table
+face-foreground syntax-table
+face-underline-p window-buffer
+file-modes window-dedicated-p
+frame-height window-display-table
+frame-parameters window-height
+frame-visible-p window-hscroll
+frame-width window-point
+get-register window-start
+getenv window-width
+global-key-binding x-get-cut-buffer
+keymap-parent x-get-cutbuffer
+local-key-binding x-get-secondary-selection
+mark x-get-selection
+mark-marker
address@hidden smallexample
+
+Most of these have directly corresponding ``set'' functions, like
address@hidden for @code{current-local-map}, or @code{goto-char}
+for @code{point}. A few, like @code{point-min}, expand to longer
+sequences of code when they are @code{setf}'d (@code{(narrow-to-region
+x (point-max))} in this case).
+
address@hidden
+A call of the form @code{(substring @var{subplace} @var{n} address@hidden)},
+where @var{subplace} is itself a valid generalized variable whose
+current value is a string, and where the value stored is also a
+string. The new string is spliced into the specified part of the
+destination string. For example:
+
address@hidden
+(setq a (list "hello" "world"))
+ @result{} ("hello" "world")
+(cadr a)
+ @result{} "world"
+(substring (cadr a) 2 4)
+ @result{} "rl"
+(setf (substring (cadr a) 2 4) "o")
+ @result{} "o"
+(cadr a)
+ @result{} "wood"
+a
+ @result{} ("hello" "wood")
address@hidden example
+
+The generalized variable @code{buffer-substring}, listed above,
+also works in this way by replacing a portion of the current buffer.
+
address@hidden
+A call of the form @code{(apply '@var{func} @dots{})} or
address@hidden(apply (function @var{func}) @dots{})}, where @var{func}
+is a @code{setf}-able function whose store function is ``suitable''
+in the sense described in Steele's book; since none of the standard
+Emacs place functions are suitable in this sense, this feature is
+only interesting when used with places you define yourself with
address@hidden or the long form of @code{defsetf}.
+
address@hidden
+A macro call, in which case the macro is expanded and @code{setf}
+is applied to the resulting form.
+
address@hidden
+Any form for which a @code{defsetf} or @code{define-setf-method}
+has been made.
address@hidden itemize
+
+Using any forms other than these in the @var{place} argument to
address@hidden will signal an error.
+
+The @code{setf} macro takes care to evaluate all subforms in
+the proper left-to-right order; for example,
+
address@hidden
+(setf (aref vec (incf i)) i)
address@hidden example
+
address@hidden
+looks like it will evaluate @code{(incf i)} exactly once, before the
+following access to @code{i}; the @code{setf} expander will insert
+temporary variables as necessary to ensure that it does in fact work
+this way no matter what setf-method is defined for @code{aref}.
+(In this case, @code{aset} would be used and no such steps would
+be necessary since @code{aset} takes its arguments in a convenient
+order.)
+
+However, if the @var{place} form is a macro which explicitly
+evaluates its arguments in an unusual order, this unusual order
+will be preserved. Adapting an example from Steele, given
+
address@hidden
+(defmacro wrong-order (x y) (list 'aref y x))
address@hidden example
+
address@hidden
+the form @code{(setf (wrong-order @var{a} @var{b}) 17)} will
+evaluate @var{b} first, then @var{a}, just as in an actual call
+to @code{wrong-order}.
address@hidden defspec
+
address@hidden Modify Macros, Customizing Setf, Basic Setf, Generalized
Variables
address@hidden Modify Macros
+
address@hidden
+This package defines a number of other macros besides @code{setf}
+that operate on generalized variables. Many are interesting and
+useful even when the @var{place} is just a variable name.
+
address@hidden psetf [place address@hidden
+This macro is to @code{setf} what @code{psetq} is to @code{setq}:
+When several @var{place}s and @var{form}s are involved, the
+assignments take place in parallel rather than sequentially.
+Specifically, all subforms are evaluated from left to right, then
+all the assignments are done (in an undefined order).
address@hidden defspec
+
address@hidden incf place &optional x
+This macro increments the number stored in @var{place} by one, or
+by @var{x} if specified. The incremented value is returned. For
+example, @code{(incf i)} is equivalent to @code{(setq i (1+ i))}, and
address@hidden(incf (car x) 2)} is equivalent to @code{(setcar x (+ (car x)
2))}.
+
+Once again, care is taken to preserve the ``apparent'' order of
+evaluation. For example,
+
address@hidden
+(incf (aref vec (incf i)))
address@hidden example
+
address@hidden
+appears to increment @code{i} once, then increment the element of
address@hidden addressed by @code{i}; this is indeed exactly what it
+does, which means the above form is @emph{not} equivalent to the
+``obvious'' expansion,
+
address@hidden
+(setf (aref vec (incf i)) (1+ (aref vec (incf i)))) ; Wrong!
address@hidden example
+
address@hidden
+but rather to something more like
+
address@hidden
+(let ((temp (incf i)))
+ (setf (aref vec temp) (1+ (aref vec temp))))
address@hidden example
+
address@hidden
+Again, all of this is taken care of automatically by @code{incf} and
+the other generalized-variable macros.
+
+As a more Emacs-specific example of @code{incf}, the expression
address@hidden(incf (point) @var{n})} is essentially equivalent to
address@hidden(forward-char @var{n})}.
address@hidden defspec
+
address@hidden decf place &optional x
+This macro decrements the number stored in @var{place} by one, or
+by @var{x} if specified.
address@hidden defspec
+
address@hidden pop place
+This macro removes and returns the first element of the list stored
+in @var{place}. It is analogous to @code{(prog1 (car @var{place})
+(setf @var{place} (cdr @var{place})))}, except that it takes care
+to evaluate all subforms only once.
address@hidden defspec
+
address@hidden push x place
+This macro inserts @var{x} at the front of the list stored in
address@hidden It is analogous to @code{(setf @var{place} (cons
address@hidden @var{place}))}, except for evaluation of the subforms.
address@hidden defspec
+
address@hidden pushnew x place @t{&key :test :test-not :key}
+This macro inserts @var{x} at the front of the list stored in
address@hidden, but only if @var{x} was not @code{eql} to any
+existing element of the list. The optional keyword arguments
+are interpreted in the same way as for @code{adjoin}.
address@hidden as Sets}.
address@hidden defspec
+
address@hidden shiftf address@hidden newvalue
+This macro shifts the @var{place}s left by one, shifting in the
+value of @var{newvalue} (which may be any Lisp expression, not just
+a generalized variable), and returning the value shifted out of
+the first @var{place}. Thus, @code{(shiftf @var{a} @var{b} @var{c}
address@hidden)} is equivalent to
+
address@hidden
+(prog1
+ @var{a}
+ (psetf @var{a} @var{b}
+ @var{b} @var{c}
+ @var{c} @var{d}))
address@hidden example
+
address@hidden
+except that the subforms of @var{a}, @var{b}, and @var{c} are actually
+evaluated only once each and in the apparent order.
address@hidden defspec
+
address@hidden rotatef address@hidden
+This macro rotates the @var{place}s left by one in circular fashion.
+Thus, @code{(rotatef @var{a} @var{b} @var{c} @var{d})} is equivalent to
+
address@hidden
+(psetf @var{a} @var{b}
+ @var{b} @var{c}
+ @var{c} @var{d}
+ @var{d} @var{a})
address@hidden example
+
address@hidden
+except for the evaluation of subforms. @code{rotatef} always
+returns @code{nil}. Note that @code{(rotatef @var{a} @var{b})}
+conveniently exchanges @var{a} and @var{b}.
address@hidden defspec
+
+The following macros were invented for this package; they have no
+analogues in Common Lisp.
+
address@hidden letf (address@hidden) address@hidden
+This macro is analogous to @code{let}, but for generalized variables
+rather than just symbols. Each @var{binding} should be of the form
address@hidden(@var{place} @var{value})}; the original contents of the
address@hidden are saved, the @var{value}s are stored in them, and
+then the body @var{form}s are executed. Afterwards, the @var{places}
+are set back to their original saved contents. This cleanup happens
+even if the @var{form}s exit irregularly due to a @code{throw} or an
+error.
+
+For example,
+
address@hidden
+(letf (((point) (point-min))
+ (a 17))
+ ...)
address@hidden example
+
address@hidden
+moves ``point'' in the current buffer to the beginning of the buffer,
+and also binds @code{a} to 17 (as if by a normal @code{let}, since
address@hidden is just a regular variable). After the body exits, @code{a}
+is set back to its original value and point is moved back to its
+original position.
+
+Note that @code{letf} on @code{(point)} is not quite like a
address@hidden, as the latter effectively saves a marker
+which tracks insertions and deletions in the buffer. Actually,
+a @code{letf} of @code{(point-marker)} is much closer to this
+behavior. (@code{point} and @code{point-marker} are equivalent
+as @code{setf} places; each will accept either an integer or a
+marker as the stored value.)
+
+Since generalized variables look like lists, @code{let}'s shorthand
+of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
+be ambiguous in @code{letf} and is not allowed.
+
+However, a @var{binding} specifier may be a one-element list
address@hidden(@var{place})}, which is similar to @samp{(@var{place}
address@hidden)}. In other words, the @var{place} is not disturbed
+on entry to the body, and the only effect of the @code{letf} is
+to restore the original value of @var{place} afterwards. (The
+redundant access-and-store suggested by the @code{(@var{place}
address@hidden)} example does not actually occur.)
+
+In most cases, the @var{place} must have a well-defined value on
+entry to the @code{letf} form. The only exceptions are plain
+variables and calls to @code{symbol-value} and @code{symbol-function}.
+If the symbol is not bound on entry, it is simply made unbound by
address@hidden or @code{fmakunbound} on exit.
address@hidden defspec
+
address@hidden letf* (address@hidden) address@hidden
+This macro is to @code{letf} what @code{let*} is to @code{let}:
+It does the bindings in sequential rather than parallel order.
address@hidden defspec
+
address@hidden callf @var{function} @var{place} @address@hidden
+This is the ``generic'' modify macro. It calls @var{function},
+which should be an unquoted function name, macro name, or lambda.
+It passes @var{place} and @var{args} as arguments, and assigns the
+result back to @var{place}. For example, @code{(incf @var{place}
address@hidden)} is the same as @code{(callf + @var{place} @var{n})}.
+Some more examples:
+
address@hidden
+(callf abs my-number)
+(callf concat (buffer-name) "<" (int-to-string n) ">")
+(callf union happy-people (list joe bob) :test 'same-person)
address@hidden example
+
address@hidden Setf}, for @code{define-modify-macro}, a way
+to create even more concise notations for modify macros. Note
+again that @code{callf} is an extension to standard Common Lisp.
address@hidden defspec
+
address@hidden callf2 @var{function} @var{arg1} @var{place} @address@hidden
+This macro is like @code{callf}, except that @var{place} is
+the @emph{second} argument of @var{function} rather than the
+first. For example, @code{(push @var{x} @var{place})} is
+equivalent to @code{(callf2 cons @var{x} @var{place})}.
address@hidden defspec
+
+The @code{callf} and @code{callf2} macros serve as building
+blocks for other macros like @code{incf}, @code{pushnew}, and
address@hidden The @code{letf} and @code{letf*}
+macros are used in the processing of symbol macros;
address@hidden Bindings}.
+
address@hidden Customizing Setf, , Modify Macros, Generalized Variables
address@hidden Customizing Setf
+
address@hidden
+Common Lisp defines three macros, @code{define-modify-macro},
address@hidden, and @code{define-setf-method}, that allow the
+user to extend generalized variables in various ways.
+
address@hidden define-modify-macro name arglist function [doc-string]
+This macro defines a ``read-modify-write'' macro similar to
address@hidden and @code{decf}. The macro @var{name} is defined
+to take a @var{place} argument followed by additional arguments
+described by @var{arglist}. The call
+
address@hidden
+(@var{name} @var{place} @var{args}...)
address@hidden example
+
address@hidden
+will be expanded to
+
address@hidden
+(callf @var{func} @var{place} @var{args}...)
address@hidden example
+
address@hidden
+which in turn is roughly equivalent to
+
address@hidden
+(setf @var{place} (@var{func} @var{place} @var{args}...))
address@hidden example
+
+For example:
+
address@hidden
+(define-modify-macro incf (&optional (n 1)) +)
+(define-modify-macro concatf (&rest args) concat)
address@hidden example
+
+Note that @code{&key} is not allowed in @var{arglist}, but
address@hidden&rest} is sufficient to pass keywords on to the function.
+
+Most of the modify macros defined by Common Lisp do not exactly
+follow the pattern of @code{define-modify-macro}. For example,
address@hidden takes its arguments in the wrong order, and @code{pop}
+is completely irregular. You can define these macros ``by hand''
+using @code{get-setf-method}, or consult the source file
address@hidden to see how to use the internal @code{setf}
+building blocks.
address@hidden defspec
+
address@hidden defsetf access-fn update-fn
+This is the simpler of two @code{defsetf} forms. Where
address@hidden is the name of a function which accesses a place,
+this declares @var{update-fn} to be the corresponding store
+function. From now on,
+
address@hidden
+(setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
address@hidden example
+
address@hidden
+will be expanded to
+
address@hidden
+(@var{update-fn} @var{arg1} @var{arg2} @var{arg3} @var{value})
address@hidden example
+
address@hidden
+The @var{update-fn} is required to be either a true function, or
+a macro which evaluates its arguments in a function-like way. Also,
+the @var{update-fn} is expected to return @var{value} as its result.
+Otherwise, the above expansion would not obey the rules for the way
address@hidden is supposed to behave.
+
+As a special (non-Common-Lisp) extension, a third argument of @code{t}
+to @code{defsetf} says that the @code{update-fn}'s return value is
+not suitable, so that the above @code{setf} should be expanded to
+something more like
+
address@hidden
+(let ((temp @var{value}))
+ (@var{update-fn} @var{arg1} @var{arg2} @var{arg3} temp)
+ temp)
address@hidden example
+
+Some examples of the use of @code{defsetf}, drawn from the standard
+suite of setf methods, are:
+
address@hidden
+(defsetf car setcar)
+(defsetf symbol-value set)
+(defsetf buffer-name rename-buffer t)
address@hidden example
address@hidden defspec
+
address@hidden defsetf access-fn arglist (store-var) address@hidden
+This is the second, more complex, form of @code{defsetf}. It is
+rather like @code{defmacro} except for the additional @var{store-var}
+argument. The @var{forms} should return a Lisp form which stores
+the value of @var{store-var} into the generalized variable formed
+by a call to @var{access-fn} with arguments described by @var{arglist}.
+The @var{forms} may begin with a string which documents the @code{setf}
+method (analogous to the doc string that appears at the front of a
+function).
+
+For example, the simple form of @code{defsetf} is shorthand for
+
address@hidden
+(defsetf @var{access-fn} (&rest args) (store)
+ (append '(@var{update-fn}) args (list store)))
address@hidden example
+
+The Lisp form that is returned can access the arguments from
address@hidden and @var{store-var} in an unrestricted fashion;
+macros like @code{setf} and @code{incf} which invoke this
+setf-method will insert temporary variables as needed to make
+sure the apparent order of evaluation is preserved.
+
+Another example drawn from the standard package:
+
address@hidden
+(defsetf nth (n x) (store)
+ (list 'setcar (list 'nthcdr n x) store))
address@hidden example
address@hidden defspec
+
address@hidden define-setf-method access-fn arglist address@hidden
+This is the most general way to create new place forms. When
+a @code{setf} to @var{access-fn} with arguments described by
address@hidden is expanded, the @var{forms} are evaluated and
+must return a list of five items:
+
address@hidden
address@hidden
+A list of @dfn{temporary variables}.
+
address@hidden
+A list of @dfn{value forms} corresponding to the temporary variables
+above. The temporary variables will be bound to these value forms
+as the first step of any operation on the generalized variable.
+
address@hidden
+A list of exactly one @dfn{store variable} (generally obtained
+from a call to @code{gensym}).
+
address@hidden
+A Lisp form which stores the contents of the store variable into
+the generalized variable, assuming the temporaries have been
+bound as described above.
+
address@hidden
+A Lisp form which accesses the contents of the generalized variable,
+assuming the temporaries have been bound.
address@hidden enumerate
+
+This is exactly like the Common Lisp macro of the same name,
+except that the method returns a list of five values rather
+than the five values themselves, since Emacs Lisp does not
+support Common Lisp's notion of multiple return values.
+
+Once again, the @var{forms} may begin with a documentation string.
+
+A setf-method should be maximally conservative with regard to
+temporary variables. In the setf-methods generated by
address@hidden, the second return value is simply the list of
+arguments in the place form, and the first return value is a
+list of a corresponding number of temporary variables generated
+by @code{gensym}. Macros like @code{setf} and @code{incf} which
+use this setf-method will optimize away most temporaries that
+turn out to be unnecessary, so there is little reason for the
+setf-method itself to optimize.
address@hidden defspec
+
address@hidden get-setf-method place &optional env
+This function returns the setf-method for @var{place}, by
+invoking the definition previously recorded by @code{defsetf}
+or @code{define-setf-method}. The result is a list of five
+values as described above. You can use this function to build
+your own @code{incf}-like modify macros. (Actually, it is
+better to use the internal functions @code{cl-setf-do-modify}
+and @code{cl-setf-do-store}, which are a bit easier to use and
+which also do a number of optimizations; consult the source
+code for the @code{incf} function for a simple example.)
+
+The argument @var{env} specifies the ``environment'' to be
+passed on to @code{macroexpand} if @code{get-setf-method} should
+need to expand a macro in @var{place}. It should come from
+an @code{&environment} argument to the macro or setf-method
+that called @code{get-setf-method}.
+
+See also the source code for the setf-methods for @code{apply}
+and @code{substring}, each of which works by calling
address@hidden on a simpler case, then massaging
+the result in various ways.
address@hidden defun
+
+Modern Common Lisp defines a second, independent way to specify
+the @code{setf} behavior of a function, namely address@hidden
+functions'' whose names are lists @code{(setf @var{name})}
+rather than symbols. For example, @code{(defun (setf foo) @dots{})}
+defines the function that is used when @code{setf} is applied to
address@hidden This package does not currently support @code{setf}
+functions. In particular, it is a compile-time error to use
address@hidden on a form which has not already been @code{defsetf}'d
+or otherwise declared; in newer Common Lisps, this would not be
+an error since the function @code{(setf @var{func})} might be
+defined later.
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Variable Bindings, Conditionals, Generalized Variables, Control
Structure
address@hidden Variable Bindings
+
address@hidden
+These Lisp forms make bindings to variables and function names,
+analogous to Lisp's built-in @code{let} form.
+
address@hidden Macros}, for the @code{letf} and @code{letf*} forms which
+are also related to variable bindings.
+
address@hidden
+* Dynamic Bindings:: The `progv' form
+* Lexical Bindings:: `lexical-let' and lexical closures
+* Function Bindings:: `flet' and `labels'
+* Macro Bindings:: `macrolet' and `symbol-macrolet'
address@hidden menu
+
address@hidden Dynamic Bindings, Lexical Bindings, Variable Bindings, Variable
Bindings
address@hidden Dynamic Bindings
+
address@hidden
+The standard @code{let} form binds variables whose names are known
+at compile-time. The @code{progv} form provides an easy way to
+bind variables whose names are computed at run-time.
+
address@hidden progv symbols values address@hidden
+This form establishes @code{let}-style variable bindings on a
+set of variables computed at run-time. The expressions
address@hidden and @var{values} are evaluated, and must return lists
+of symbols and values, respectively. The symbols are bound to the
+corresponding values for the duration of the body @var{form}s.
+If @var{values} is shorter than @var{symbols}, the last few symbols
+are made unbound (as if by @code{makunbound}) inside the body.
+If @var{symbols} is shorter than @var{values}, the excess values
+are ignored.
address@hidden defspec
+
address@hidden Lexical Bindings, Function Bindings, Dynamic Bindings, Variable
Bindings
address@hidden Lexical Bindings
+
address@hidden
+The @dfn{CL} package defines the following macro which
+more closely follows the Common Lisp @code{let} form:
+
address@hidden lexical-let (address@hidden) address@hidden
+This form is exactly like @code{let} except that the bindings it
+establishes are purely lexical. Lexical bindings are similar to
+local variables in a language like C: Only the code physically
+within the body of the @code{lexical-let} (after macro expansion)
+may refer to the bound variables.
+
address@hidden
+(setq a 5)
+(defun foo (b) (+ a b))
+(let ((a 2)) (foo a))
+ @result{} 4
+(lexical-let ((a 2)) (foo a))
+ @result{} 7
address@hidden example
+
address@hidden
+In this example, a regular @code{let} binding of @code{a} actually
+makes a temporary change to the global variable @code{a}, so @code{foo}
+is able to see the binding of @code{a} to 2. But @code{lexical-let}
+actually creates a distinct local variable @code{a} for use within its
+body, without any effect on the global variable of the same name.
+
+The most important use of lexical bindings is to create @dfn{closures}.
+A closure is a function object that refers to an outside lexical
+variable. For example:
+
address@hidden
+(defun make-adder (n)
+ (lexical-let ((n n))
+ (function (lambda (m) (+ n m)))))
+(setq add17 (make-adder 17))
+(funcall add17 4)
+ @result{} 21
address@hidden example
+
address@hidden
+The call @code{(make-adder 17)} returns a function object which adds
+17 to its argument. If @code{let} had been used instead of
address@hidden, the function object would have referred to the
+global @code{n}, which would have been bound to 17 only during the
+call to @code{make-adder} itself.
+
address@hidden
+(defun make-counter ()
+ (lexical-let ((n 0))
+ (function* (lambda (&optional (m 1)) (incf n m)))))
+(setq count-1 (make-counter))
+(funcall count-1 3)
+ @result{} 3
+(funcall count-1 14)
+ @result{} 17
+(setq count-2 (make-counter))
+(funcall count-2 5)
+ @result{} 5
+(funcall count-1 2)
+ @result{} 19
+(funcall count-2)
+ @result{} 6
address@hidden example
+
address@hidden
+Here we see that each call to @code{make-counter} creates a distinct
+local variable @code{n}, which serves as a private counter for the
+function object that is returned.
+
+Closed-over lexical variables persist until the last reference to
+them goes away, just like all other Lisp objects. For example,
address@hidden refers to a function object which refers to an
+instance of the variable @code{n}; this is the only reference
+to that variable, so after @code{(setq count-2 nil)} the garbage
+collector would be able to delete this instance of @code{n}.
+Of course, if a @code{lexical-let} does not actually create any
+closures, then the lexical variables are free as soon as the
address@hidden returns.
+
+Many closures are used only during the extent of the bindings they
+refer to; these are known as ``downward funargs'' in Lisp parlance.
+When a closure is used in this way, regular Emacs Lisp dynamic
+bindings suffice and will be more efficient than @code{lexical-let}
+closures:
+
address@hidden
+(defun add-to-list (x list)
+ (mapcar (lambda (y) (+ x y))) list)
+(add-to-list 7 '(1 2 5))
+ @result{} (8 9 12)
address@hidden example
+
address@hidden
+Since this lambda is only used while @code{x} is still bound,
+it is not necessary to make a true closure out of it.
+
+You can use @code{defun} or @code{flet} inside a @code{lexical-let}
+to create a named closure. If several closures are created in the
+body of a single @code{lexical-let}, they all close over the same
+instance of the lexical variable.
+
+The @code{lexical-let} form is an extension to Common Lisp. In
+true Common Lisp, all bindings are lexical unless declared otherwise.
address@hidden defspec
+
address@hidden lexical-let* (address@hidden) address@hidden
+This form is just like @code{lexical-let}, except that the bindings
+are made sequentially in the manner of @code{let*}.
address@hidden defspec
+
address@hidden Function Bindings, Macro Bindings, Lexical Bindings, Variable
Bindings
address@hidden Function Bindings
+
address@hidden
+These forms make @code{let}-like bindings to functions instead
+of variables.
+
address@hidden flet (address@hidden) address@hidden
+This form establishes @code{let}-style bindings on the function
+cells of symbols rather than on the value cells. Each @var{binding}
+must be a list of the form @samp{(@var{name} @var{arglist}
address@hidden@dots{})}, which defines a function exactly as if
+it were a @code{defun*} form. The function @var{name} is defined
+accordingly for the duration of the body of the @code{flet}; then
+the old function definition, or lack thereof, is restored.
+
+While @code{flet} in Common Lisp establishes a lexical binding of
address@hidden, Emacs Lisp @code{flet} makes a dynamic binding. The
+result is that @code{flet} affects indirect calls to a function as
+well as calls directly inside the @code{flet} form itself.
+
+You can use @code{flet} to disable or modify the behavior of a
+function in a temporary fashion. This will even work on Emacs
+primitives, although note that some calls to primitive functions
+internal to Emacs are made without going through the symbol's
+function cell, and so will not be affected by @code{flet}. For
+example,
+
address@hidden
+(flet ((message (&rest args) (push args saved-msgs)))
+ (do-something))
address@hidden example
+
+This code attempts to replace the built-in function @code{message}
+with a function that simply saves the messages in a list rather
+than displaying them. The original definition of @code{message}
+will be restored after @code{do-something} exits. This code will
+work fine on messages generated by other Lisp code, but messages
+generated directly inside Emacs will not be caught since they make
+direct C-language calls to the message routines rather than going
+through the Lisp @code{message} function.
+
+Functions defined by @code{flet} may use the full Common Lisp
+argument notation supported by @code{defun*}; also, the function
+body is enclosed in an implicit block as if by @code{defun*}.
address@hidden Structure}.
address@hidden defspec
+
address@hidden labels (address@hidden) address@hidden
+The @code{labels} form is like @code{flet}, except that it
+makes lexical bindings of the function names rather than
+dynamic bindings. (In true Common Lisp, both @code{flet} and
address@hidden make lexical bindings of slightly different sorts;
+since Emacs Lisp is dynamically bound by default, it seemed
+more appropriate for @code{flet} also to use dynamic binding.
+The @code{labels} form, with its lexical binding, is fully
+compatible with Common Lisp.)
+
+Lexical scoping means that all references to the named
+functions must appear physically within the body of the
address@hidden form. References may appear both in the body
address@hidden of @code{labels} itself, and in the bodies of
+the functions themselves. Thus, @code{labels} can define
+local recursive functions, or mutually-recursive sets of
+functions.
+
+A ``reference'' to a function name is either a call to that
+function, or a use of its name quoted by @code{quote} or
address@hidden to be passed on to, say, @code{mapcar}.
address@hidden defspec
+
address@hidden Macro Bindings, , Function Bindings, Variable Bindings
address@hidden Macro Bindings
+
address@hidden
+These forms create local macros and ``symbol macros.''
+
address@hidden macrolet (address@hidden) address@hidden
+This form is analogous to @code{flet}, but for macros instead of
+functions. Each @var{binding} is a list of the same form as the
+arguments to @code{defmacro*} (i.e., a macro name, argument list,
+and macro-expander forms). The macro is defined accordingly for
+use within the body of the @code{macrolet}.
+
+Because of the nature of macros, @code{macrolet} is lexically
+scoped even in Emacs Lisp: The @code{macrolet} binding will
+affect only calls that appear physically within the body
address@hidden, possibly after expansion of other macros in the
+body.
address@hidden defspec
+
address@hidden symbol-macrolet (address@hidden) address@hidden
+This form creates @dfn{symbol macros}, which are macros that look
+like variable references rather than function calls. Each
address@hidden is a list @samp{(@var{var} @var{expansion})};
+any reference to @var{var} within the body @var{forms} is
+replaced by @var{expansion}.
+
address@hidden
+(setq bar '(5 . 9))
+(symbol-macrolet ((foo (car bar)))
+ (incf foo))
+bar
+ @result{} (6 . 9)
address@hidden example
+
+A @code{setq} of a symbol macro is treated the same as a @code{setf}.
+I.e., @code{(setq foo 4)} in the above would be equivalent to
address@hidden(setf foo 4)}, which in turn expands to @code{(setf (car bar) 4)}.
+
+Likewise, a @code{let} or @code{let*} binding a symbol macro is
+treated like a @code{letf} or @code{letf*}. This differs from true
+Common Lisp, where the rules of lexical scoping cause a @code{let}
+binding to shadow a @code{symbol-macrolet} binding. In this package,
+only @code{lexical-let} and @code{lexical-let*} will shadow a symbol
+macro.
+
+There is no analogue of @code{defmacro} for symbol macros; all symbol
+macros are local. A typical use of @code{symbol-macrolet} is in the
+expansion of another macro:
+
address@hidden
+(defmacro* my-dolist ((x list) &rest body)
+ (let ((var (gensym)))
+ (list 'loop 'for var 'on list 'do
+ (list* 'symbol-macrolet (list (list x (list 'car var)))
+ body))))
+
+(setq mylist '(1 2 3 4))
+(my-dolist (x mylist) (incf x))
+mylist
+ @result{} (2 3 4 5)
address@hidden example
+
address@hidden
+In this example, the @code{my-dolist} macro is similar to @code{dolist}
+(@pxref{Iteration}) except that the variable @code{x} becomes a true
+reference onto the elements of the list. The @code{my-dolist} call
+shown here expands to
+
address@hidden
+(loop for G1234 on mylist do
+ (symbol-macrolet ((x (car G1234)))
+ (incf x)))
address@hidden example
+
address@hidden
+which in turn expands to
+
address@hidden
+(loop for G1234 on mylist do (incf (car G1234)))
address@hidden example
+
address@hidden Facility}, for a description of the @code{loop} macro.
+This package defines a nonstandard @code{in-ref} loop clause that
+works much like @code{my-dolist}.
address@hidden defspec
+
address@hidden Conditionals, Blocks and Exits, Variable Bindings, Control
Structure
address@hidden Conditionals
+
address@hidden
+These conditional forms augment Emacs Lisp's simple @code{if},
address@hidden, @code{or}, and @code{cond} forms.
+
address@hidden case keyform address@hidden
+This macro evaluates @var{keyform}, then compares it with the key
+values listed in the various @var{clause}s. Whichever clause matches
+the key is executed; comparison is done by @code{eql}. If no clause
+matches, the @code{case} form returns @code{nil}. The clauses are
+of the form
+
address@hidden
+(@var{keylist} @address@hidden)
address@hidden example
+
address@hidden
+where @var{keylist} is a list of key values. If there is exactly
+one value, and it is not a cons cell or the symbol @code{nil} or
address@hidden, then it can be used by itself as a @var{keylist} without
+being enclosed in a list. All key values in the @code{case} form
+must be distinct. The final clauses may use @code{t} in place of
+a @var{keylist} to indicate a default clause that should be taken
+if none of the other clauses match. (The symbol @code{otherwise}
+is also recognized in place of @code{t}. To make a clause that
+matches the actual symbol @code{t}, @code{nil}, or @code{otherwise},
+enclose the symbol in a list.)
+
+For example, this expression reads a keystroke, then does one of
+four things depending on whether it is an @samp{a}, a @samp{b},
+a @key{RET} or @kbd{C-j}, or anything else.
+
address@hidden
+(case (read-char)
+ (?a (do-a-thing))
+ (?b (do-b-thing))
+ ((?\r ?\n) (do-ret-thing))
+ (t (do-other-thing)))
address@hidden example
address@hidden defspec
+
address@hidden ecase keyform address@hidden
+This macro is just like @code{case}, except that if the key does
+not match any of the clauses, an error is signaled rather than
+simply returning @code{nil}.
address@hidden defspec
+
address@hidden typecase keyform address@hidden
+This macro is a version of @code{case} that checks for types
+rather than values. Each @var{clause} is of the form
address@hidden(@var{type} @var{body}...)}. @xref{Type Predicates},
+for a description of type specifiers. For example,
+
address@hidden
+(typecase x
+ (integer (munch-integer x))
+ (float (munch-float x))
+ (string (munch-integer (string-to-int x)))
+ (t (munch-anything x)))
address@hidden example
+
+The type specifier @code{t} matches any type of object; the word
address@hidden is also allowed. To make one clause match any of
+several types, use an @code{(or ...)} type specifier.
address@hidden defspec
+
address@hidden etypecase keyform address@hidden
+This macro is just like @code{typecase}, except that if the key does
+not match any of the clauses, an error is signaled rather than
+simply returning @code{nil}.
address@hidden defspec
+
address@hidden Blocks and Exits, Iteration, Conditionals, Control Structure
address@hidden Blocks and Exits
+
address@hidden
+Common Lisp @dfn{blocks} provide a non-local exit mechanism very
+similar to @code{catch} and @code{throw}, but lexically rather than
+dynamically scoped. This package actually implements @code{block}
+in terms of @code{catch}; however, the lexical scoping allows the
+optimizing byte-compiler to omit the costly @code{catch} step if the
+body of the block does not actually @code{return-from} the block.
+
address@hidden block name address@hidden
+The @var{forms} are evaluated as if by a @code{progn}. However,
+if any of the @var{forms} execute @code{(return-from @var{name})},
+they will jump out and return directly from the @code{block} form.
+The @code{block} returns the result of the last @var{form} unless
+a @code{return-from} occurs.
+
+The @code{block}/@code{return-from} mechanism is quite similar to
+the @code{catch}/@code{throw} mechanism. The main differences are
+that block @var{name}s are unevaluated symbols, rather than forms
+(such as quoted symbols) which evaluate to a tag at run-time; and
+also that blocks are lexically scoped whereas @code{catch}/@code{throw}
+are dynamically scoped. This means that functions called from the
+body of a @code{catch} can also @code{throw} to the @code{catch},
+but the @code{return-from} referring to a block name must appear
+physically within the @var{forms} that make up the body of the block.
+They may not appear within other called functions, although they may
+appear within macro expansions or @code{lambda}s in the body. Block
+names and @code{catch} names form independent name-spaces.
+
+In true Common Lisp, @code{defun} and @code{defmacro} surround
+the function or expander bodies with implicit blocks with the
+same name as the function or macro. This does not occur in Emacs
+Lisp, but this package provides @code{defun*} and @code{defmacro*}
+forms which do create the implicit block.
+
+The Common Lisp looping constructs defined by this package,
+such as @code{loop} and @code{dolist}, also create implicit blocks
+just as in Common Lisp.
+
+Because they are implemented in terms of Emacs Lisp @code{catch}
+and @code{throw}, blocks have the same overhead as actual
address@hidden constructs (roughly two function calls). However,
+the optimizing byte compiler will optimize away the @code{catch}
+if the block does
+not in fact contain any @code{return} or @code{return-from} calls
+that jump to it. This means that @code{do} loops and @code{defun*}
+functions which don't use @code{return} don't pay the overhead to
+support it.
address@hidden defspec
+
address@hidden return-from name [result]
+This macro returns from the block named @var{name}, which must be
+an (unevaluated) symbol. If a @var{result} form is specified, it
+is evaluated to produce the result returned from the @code{block}.
+Otherwise, @code{nil} is returned.
address@hidden defspec
+
address@hidden return [result]
+This macro is exactly like @code{(return-from nil @var{result})}.
+Common Lisp loops like @code{do} and @code{dolist} implicitly enclose
+themselves in @code{nil} blocks.
address@hidden defspec
+
address@hidden Iteration, Loop Facility, Blocks and Exits, Control Structure
address@hidden Iteration
+
address@hidden
+The macros described here provide more sophisticated, high-level
+looping constructs to complement Emacs Lisp's basic @code{while}
+loop.
+
address@hidden loop address@hidden
+The @dfn{CL} package supports both the simple, old-style meaning of
address@hidden and the extremely powerful and flexible feature known as
+the @dfn{Loop Facility} or @dfn{Loop Macro}. This more advanced
+facility is discussed in the following section; @pxref{Loop Facility}.
+The simple form of @code{loop} is described here.
+
+If @code{loop} is followed by zero or more Lisp expressions,
+then @code{(loop @address@hidden)} simply creates an infinite
+loop executing the expressions over and over. The loop is
+enclosed in an implicit @code{nil} block. Thus,
+
address@hidden
+(loop (foo) (if (no-more) (return 72)) (bar))
address@hidden example
+
address@hidden
+is exactly equivalent to
+
address@hidden
+(block nil (while t (foo) (if (no-more) (return 72)) (bar)))
address@hidden example
+
+If any of the expressions are plain symbols, the loop is instead
+interpreted as a Loop Macro specification as described later.
+(This is not a restriction in practice, since a plain symbol
+in the above notation would simply access and throw away the
+value of a variable.)
address@hidden defspec
+
address@hidden do (address@hidden) (end-test address@hidden) address@hidden
+This macro creates a general iterative loop. Each @var{spec} is
+of the form
+
address@hidden
+(@var{var} address@hidden address@hidden)
address@hidden example
+
+The loop works as follows: First, each @var{var} is bound to the
+associated @var{init} value as if by a @code{let} form. Then, in
+each iteration of the loop, the @var{end-test} is evaluated; if
+true, the loop is finished. Otherwise, the body @var{forms} are
+evaluated, then each @var{var} is set to the associated @var{step}
+expression (as if by a @code{psetq} form) and the next iteration
+begins. Once the @var{end-test} becomes true, the @var{result}
+forms are evaluated (with the @var{var}s still bound to their
+values) to produce the result returned by @code{do}.
+
+The entire @code{do} loop is enclosed in an implicit @code{nil}
+block, so that you can use @code{(return)} to break out of the
+loop at any time.
+
+If there are no @var{result} forms, the loop returns @code{nil}.
+If a given @var{var} has no @var{step} form, it is bound to its
address@hidden value but not otherwise modified during the @code{do}
+loop (unless the code explicitly modifies it); this case is just
+a shorthand for putting a @code{(let ((@var{var} @var{init})) @dots{})}
+around the loop. If @var{init} is also omitted it defaults to
address@hidden, and in this case a plain @address@hidden can be used
+in place of @samp{(@var{var})}, again following the analogy with
address@hidden
+
+This example (from Steele) illustrates a loop which applies the
+function @code{f} to successive pairs of values from the lists
address@hidden and @code{bar}; it is equivalent to the call
address@hidden(mapcar* 'f foo bar)}. Note that this loop has no body
address@hidden at all, performing all its work as side effects of
+the rest of the loop.
+
address@hidden
+(do ((x foo (cdr x))
+ (y bar (cdr y))
+ (z nil (cons (f (car x) (car y)) z)))
+ ((or (null x) (null y))
+ (nreverse z)))
address@hidden example
address@hidden defspec
+
address@hidden do* (address@hidden) (end-test address@hidden) address@hidden
+This is to @code{do} what @code{let*} is to @code{let}. In
+particular, the initial values are bound as if by @code{let*}
+rather than @code{let}, and the steps are assigned as if by
address@hidden rather than @code{psetq}.
+
+Here is another way to write the above loop:
+
address@hidden
+(do* ((xp foo (cdr xp))
+ (yp bar (cdr yp))
+ (x (car xp) (car xp))
+ (y (car yp) (car yp))
+ z)
+ ((or (null xp) (null yp))
+ (nreverse z))
+ (push (f x y) z))
address@hidden example
address@hidden defspec
+
address@hidden dolist (var list [result]) address@hidden
+This is a more specialized loop which iterates across the elements
+of a list. @var{list} should evaluate to a list; the body @var{forms}
+are executed with @var{var} bound to each element of the list in
+turn. Finally, the @var{result} form (or @code{nil}) is evaluated
+with @var{var} bound to @code{nil} to produce the result returned by
+the loop. Unlike with Emacs's built in @code{dolist}, the loop is
+surrounded by an implicit @code{nil} block.
address@hidden defspec
+
address@hidden dotimes (var count [result]) address@hidden
+This is a more specialized loop which iterates a specified number
+of times. The body is executed with @var{var} bound to the integers
+from zero (inclusive) to @var{count} (exclusive), in turn. Then
+the @code{result} form is evaluated with @var{var} bound to the total
+number of iterations that were done (i.e., @code{(max 0 @var{count})})
+to get the return value for the loop form. Unlike with Emacs's built in
address@hidden, the loop is surrounded by an implicit @code{nil} block.
address@hidden defspec
+
address@hidden do-symbols (var [obarray [result]]) address@hidden
+This loop iterates over all interned symbols. If @var{obarray}
+is specified and is not @code{nil}, it loops over all symbols in
+that obarray. For each symbol, the body @var{forms} are evaluated
+with @var{var} bound to that symbol. The symbols are visited in
+an unspecified order. Afterward the @var{result} form, if any,
+is evaluated (with @var{var} bound to @code{nil}) to get the return
+value. The loop is surrounded by an implicit @code{nil} block.
address@hidden defspec
+
address@hidden do-all-symbols (var [result]) address@hidden
+This is identical to @code{do-symbols} except that the @var{obarray}
+argument is omitted; it always iterates over the default obarray.
address@hidden defspec
+
address@hidden over Sequences}, for some more functions for
+iterating over vectors or lists.
+
address@hidden Loop Facility, Multiple Values, Iteration, Control Structure
address@hidden Loop Facility
+
address@hidden
+A common complaint with Lisp's traditional looping constructs is
+that they are either too simple and limited, such as Common Lisp's
address@hidden or Emacs Lisp's @code{while}, or too unreadable and
+obscure, like Common Lisp's @code{do} loop.
+
+To remedy this, recent versions of Common Lisp have added a new
+construct called the ``Loop Facility'' or address@hidden macro,''
+with an easy-to-use but very powerful and expressive syntax.
+
address@hidden
+* Loop Basics:: `loop' macro, basic clause structure
+* Loop Examples:: Working examples of `loop' macro
+* For Clauses:: Clauses introduced by `for' or `as'
+* Iteration Clauses:: `repeat', `while', `thereis', etc.
+* Accumulation Clauses:: `collect', `sum', `maximize', etc.
+* Other Clauses:: `with', `if', `initially', `finally'
address@hidden menu
+
address@hidden Loop Basics, Loop Examples, Loop Facility, Loop Facility
address@hidden Loop Basics
+
address@hidden
+The @code{loop} macro essentially creates a mini-language within
+Lisp that is specially tailored for describing loops. While this
+language is a little strange-looking by the standards of regular Lisp,
+it turns out to be very easy to learn and well-suited to its purpose.
+
+Since @code{loop} is a macro, all parsing of the loop language
+takes place at byte-compile time; compiled @code{loop}s are just
+as efficient as the equivalent @code{while} loops written longhand.
+
address@hidden loop address@hidden
+A loop construct consists of a series of @var{clause}s, each
+introduced by a symbol like @code{for} or @code{do}. Clauses
+are simply strung together in the argument list of @code{loop},
+with minimal extra parentheses. The various types of clauses
+specify initializations, such as the binding of temporary
+variables, actions to be taken in the loop, stepping actions,
+and final cleanup.
+
+Common Lisp specifies a certain general order of clauses in a
+loop:
+
address@hidden
+(loop @var{name-clause}
+ @address@hidden
+ @address@hidden)
address@hidden example
+
+The @var{name-clause} optionally gives a name to the implicit
+block that surrounds the loop. By default, the implicit block
+is named @code{nil}. The @var{var-clauses} specify what
+variables should be bound during the loop, and how they should
+be modified or iterated throughout the course of the loop. The
address@hidden are things to be done during the loop, such
+as computing, collecting, and returning values.
+
+The Emacs version of the @code{loop} macro is less restrictive about
+the order of clauses, but things will behave most predictably if
+you put the variable-binding clauses @code{with}, @code{for}, and
address@hidden before the action clauses. As in Common Lisp,
address@hidden and @code{finally} clauses can go anywhere.
+
+Loops generally return @code{nil} by default, but you can cause
+them to return a value by using an accumulation clause like
address@hidden, an end-test clause like @code{always}, or an
+explicit @code{return} clause to jump out of the implicit block.
+(Because the loop body is enclosed in an implicit block, you can
+also use regular Lisp @code{return} or @code{return-from} to
+break out of the loop.)
address@hidden defspec
+
+The following sections give some examples of the Loop Macro in
+action, and describe the particular loop clauses in great detail.
+Consult the second edition of Steele's @dfn{Common Lisp, the Language},
+for additional discussion and examples of the @code{loop} macro.
+
address@hidden Loop Examples, For Clauses, Loop Basics, Loop Facility
address@hidden Loop Examples
+
address@hidden
+Before listing the full set of clauses that are allowed, let's
+look at a few example loops just to get a feel for the @code{loop}
+language.
+
address@hidden
+(loop for buf in (buffer-list)
+ collect (buffer-file-name buf))
address@hidden example
+
address@hidden
+This loop iterates over all Emacs buffers, using the list
+returned by @code{buffer-list}. For each buffer @code{buf},
+it calls @code{buffer-file-name} and collects the results into
+a list, which is then returned from the @code{loop} construct.
+The result is a list of the file names of all the buffers in
+Emacs' memory. The words @code{for}, @code{in}, and @code{collect}
+are reserved words in the @code{loop} language.
+
address@hidden
+(loop repeat 20 do (insert "Yowsa\n"))
address@hidden example
+
address@hidden
+This loop inserts the phrase ``Yowsa'' twenty times in the
+current buffer.
+
address@hidden
+(loop until (eobp) do (munch-line) (forward-line 1))
address@hidden example
+
address@hidden
+This loop calls @code{munch-line} on every line until the end
+of the buffer. If point is already at the end of the buffer,
+the loop exits immediately.
+
address@hidden
+(loop do (munch-line) until (eobp) do (forward-line 1))
address@hidden example
+
address@hidden
+This loop is similar to the above one, except that @code{munch-line}
+is always called at least once.
+
address@hidden
+(loop for x from 1 to 100
+ for y = (* x x)
+ until (>= y 729)
+ finally return (list x (= y 729)))
address@hidden example
+
address@hidden
+This more complicated loop searches for a number @code{x} whose
+square is 729. For safety's sake it only examines @code{x}
+values up to 100; dropping the phrase @samp{to 100} would
+cause the loop to count upwards with no limit. The second
address@hidden clause defines @code{y} to be the square of @code{x}
+within the loop; the expression after the @code{=} sign is
+reevaluated each time through the loop. The @code{until}
+clause gives a condition for terminating the loop, and the
address@hidden clause says what to do when the loop finishes.
+(This particular example was written less concisely than it
+could have been, just for the sake of illustration.)
+
+Note that even though this loop contains three clauses (two
address@hidden and an @code{until}) that would have been enough to
+define loops all by themselves, it still creates a single loop
+rather than some sort of triple-nested loop. You must explicitly
+nest your @code{loop} constructs if you want nested loops.
+
address@hidden For Clauses, Iteration Clauses, Loop Examples, Loop Facility
address@hidden For Clauses
+
address@hidden
+Most loops are governed by one or more @code{for} clauses.
+A @code{for} clause simultaneously describes variables to be
+bound, how those variables are to be stepped during the loop,
+and usually an end condition based on those variables.
+
+The word @code{as} is a synonym for the word @code{for}. This
+word is followed by a variable name, then a word like @code{from}
+or @code{across} that describes the kind of iteration desired.
+In Common Lisp, the phrase @code{being the} sometimes precedes
+the type of iteration; in this package both @code{being} and
address@hidden are optional. The word @code{each} is a synonym
+for @code{the}, and the word that follows it may be singular
+or plural: @samp{for x being the elements of y} or
address@hidden x being each element of y}. Which form you use
+is purely a matter of style.
+
+The variable is bound around the loop as if by @code{let}:
+
address@hidden
+(setq i 'happy)
+(loop for i from 1 to 10 do (do-something-with i))
+i
+ @result{} happy
address@hidden example
+
address@hidden @code
address@hidden for @var{var} from @var{expr1} to @var{expr2} by @var{expr3}
+This type of @code{for} clause creates a counting loop. Each of
+the three sub-terms is optional, though there must be at least one
+term so that the clause is marked as a counting clause.
+
+The three expressions are the starting value, the ending value, and
+the step value, respectively, of the variable. The loop counts
+upwards by default (@var{expr3} must be positive), from @var{expr1}
+to @var{expr2} inclusively. If you omit the @code{from} term, the
+loop counts from zero; if you omit the @code{to} term, the loop
+counts forever without stopping (unless stopped by some other
+loop clause, of course); if you omit the @code{by} term, the loop
+counts in steps of one.
+
+You can replace the word @code{from} with @code{upfrom} or
address@hidden to indicate the direction of the loop. Likewise,
+you can replace @code{to} with @code{upto} or @code{downto}.
+For example, @samp{for x from 5 downto 1} executes five times
+with @code{x} taking on the integers from 5 down to 1 in turn.
+Also, you can replace @code{to} with @code{below} or @code{above},
+which are like @code{upto} and @code{downto} respectively except
+that they are exclusive rather than inclusive limits:
+
address@hidden
+(loop for x to 10 collect x)
+ @result{} (0 1 2 3 4 5 6 7 8 9 10)
+(loop for x below 10 collect x)
+ @result{} (0 1 2 3 4 5 6 7 8 9)
address@hidden example
+
+The @code{by} value is always positive, even for downward-counting
+loops. Some sort of @code{from} value is required for downward
+loops; @samp{for x downto 5} is not a valid loop clause all by
+itself.
+
address@hidden for @var{var} in @var{list} by @var{function}
+This clause iterates @var{var} over all the elements of @var{list},
+in turn. If you specify the @code{by} term, then @var{function}
+is used to traverse the list instead of @code{cdr}; it must be a
+function taking one argument. For example:
+
address@hidden
+(loop for x in '(1 2 3 4 5 6) collect (* x x))
+ @result{} (1 4 9 16 25 36)
+(loop for x in '(1 2 3 4 5 6) by 'cddr collect (* x x))
+ @result{} (1 9 25)
address@hidden example
+
address@hidden for @var{var} on @var{list} by @var{function}
+This clause iterates @var{var} over all the cons cells of @var{list}.
+
address@hidden
+(loop for x on '(1 2 3 4) collect x)
+ @result{} ((1 2 3 4) (2 3 4) (3 4) (4))
address@hidden example
+
+With @code{by}, there is no real reason that the @code{on} expression
+must be a list. For example:
+
address@hidden
+(loop for x on first-animal by 'next-animal collect x)
address@hidden example
+
address@hidden
+where @code{(next-animal x)} takes an ``animal'' @var{x} and returns
+the next in the (assumed) sequence of animals, or @code{nil} if
address@hidden was the last animal in the sequence.
+
address@hidden for @var{var} in-ref @var{list} by @var{function}
+This is like a regular @code{in} clause, but @var{var} becomes
+a @code{setf}-able ``reference'' onto the elements of the list
+rather than just a temporary variable. For example,
+
address@hidden
+(loop for x in-ref my-list do (incf x))
address@hidden example
+
address@hidden
+increments every element of @code{my-list} in place. This clause
+is an extension to standard Common Lisp.
+
address@hidden for @var{var} across @var{array}
+This clause iterates @var{var} over all the elements of @var{array},
+which may be a vector or a string.
+
address@hidden
+(loop for x across "aeiou"
+ do (use-vowel (char-to-string x)))
address@hidden example
+
address@hidden for @var{var} across-ref @var{array}
+This clause iterates over an array, with @var{var} a @code{setf}-able
+reference onto the elements; see @code{in-ref} above.
+
address@hidden for @var{var} being the elements of @var{sequence}
+This clause iterates over the elements of @var{sequence}, which may
+be a list, vector, or string. Since the type must be determined
+at run-time, this is somewhat less efficient than @code{in} or
address@hidden The clause may be followed by the additional term
address@hidden (index @var{var2})} to cause @var{var2} to be bound to
+the successive indices (starting at 0) of the elements.
+
+This clause type is taken from older versions of the @code{loop} macro,
+and is not present in modern Common Lisp. The @samp{using (sequence ...)}
+term of the older macros is not supported.
+
address@hidden for @var{var} being the elements of-ref @var{sequence}
+This clause iterates over a sequence, with @var{var} a @code{setf}-able
+reference onto the elements; see @code{in-ref} above.
+
address@hidden for @var{var} being the symbols [of @var{obarray}]
+This clause iterates over symbols, either over all interned symbols
+or over all symbols in @var{obarray}. The loop is executed with
address@hidden bound to each symbol in turn. The symbols are visited in
+an unspecified order.
+
+As an example,
+
address@hidden
+(loop for sym being the symbols
+ when (fboundp sym)
+ when (string-match "^map" (symbol-name sym))
+ collect sym)
address@hidden example
+
address@hidden
+returns a list of all the functions whose names begin with @samp{map}.
+
+The Common Lisp words @code{external-symbols} and @code{present-symbols}
+are also recognized but are equivalent to @code{symbols} in Emacs Lisp.
+
+Due to a minor implementation restriction, it will not work to have
+more than one @code{for} clause iterating over symbols, hash tables,
+keymaps, overlays, or intervals in a given @code{loop}. Fortunately,
+it would rarely if ever be useful to do so. It @emph{is} valid to mix
+one of these types of clauses with other clauses like @code{for ... to}
+or @code{while}.
+
address@hidden for @var{var} being the hash-keys of @var{hash-table}
+This clause iterates over the entries in @var{hash-table}. For each
+hash table entry, @var{var} is bound to the entry's key. If you write
address@hidden hash-values} instead, @var{var} is bound to the values
+of the entries. The clause may be followed by the additional
+term @samp{using (hash-values @var{var2})} (where @code{hash-values}
+is the opposite word of the word following @code{the}) to cause
address@hidden and @var{var2} to be bound to the two parts of each
+hash table entry.
+
address@hidden for @var{var} being the key-codes of @var{keymap}
+This clause iterates over the entries in @var{keymap}.
+The iteration does not enter nested keymaps or inherited (parent) keymaps.
+You can use @samp{the key-bindings} to access the commands bound to
+the keys rather than the key codes, and you can add a @code{using}
+clause to access both the codes and the bindings together.
+
address@hidden for @var{var} being the key-seqs of @var{keymap}
+This clause iterates over all key sequences defined by @var{keymap}
+and its nested keymaps, where @var{var} takes on values which are
+vectors. The strings or vectors
+are reused for each iteration, so you must copy them if you wish to keep
+them permanently. You can add a @samp{using (key-bindings ...)}
+clause to get the command bindings as well.
+
address@hidden for @var{var} being the overlays [of @var{buffer}] @dots{}
+This clause iterates over the ``overlays'' of a buffer
+(the clause @code{extents} is synonymous
+with @code{overlays}). If the @code{of} term is omitted, the current
+buffer is used.
+This clause also accepts optional @samp{from @var{pos}} and
address@hidden @var{pos}} terms, limiting the clause to overlays which
+overlap the specified region.
+
address@hidden for @var{var} being the intervals [of @var{buffer}] @dots{}
+This clause iterates over all intervals of a buffer with constant
+text properties. The variable @var{var} will be bound to conses
+of start and end positions, where one start position is always equal
+to the previous end position. The clause allows @code{of},
address@hidden, @code{to}, and @code{property} terms, where the latter
+term restricts the search to just the specified property. The
address@hidden term may specify either a buffer or a string.
+
address@hidden for @var{var} being the frames
+This clause iterates over all frames, i.e., X window system windows
+open on Emacs files. The
+clause @code{screens} is a synonym for @code{frames}. The frames
+are visited in @code{next-frame} order starting from
address@hidden
+
address@hidden for @var{var} being the windows [of @var{frame}]
+This clause iterates over the windows (in the Emacs sense) of
+the current frame, or of the specified @var{frame}.
+
address@hidden for @var{var} being the buffers
+This clause iterates over all buffers in Emacs. It is equivalent
+to @samp{for @var{var} in (buffer-list)}.
+
address@hidden for @var{var} = @var{expr1} then @var{expr2}
+This clause does a general iteration. The first time through
+the loop, @var{var} will be bound to @var{expr1}. On the second
+and successive iterations it will be set by evaluating @var{expr2}
+(which may refer to the old value of @var{var}). For example,
+these two loops are effectively the same:
+
address@hidden
+(loop for x on my-list by 'cddr do ...)
+(loop for x = my-list then (cddr x) while x do ...)
address@hidden example
+
+Note that this type of @code{for} clause does not imply any sort
+of terminating condition; the above example combines it with a
address@hidden clause to tell when to end the loop.
+
+If you omit the @code{then} term, @var{expr1} is used both for
+the initial setting and for successive settings:
+
address@hidden
+(loop for x = (random) when (> x 0) return x)
address@hidden example
+
address@hidden
+This loop keeps taking random numbers from the @code{(random)}
+function until it gets a positive one, which it then returns.
address@hidden table
+
+If you include several @code{for} clauses in a row, they are
+treated sequentially (as if by @code{let*} and @code{setq}).
+You can instead use the word @code{and} to link the clauses,
+in which case they are processed in parallel (as if by @code{let}
+and @code{psetq}).
+
address@hidden
+(loop for x below 5 for y = nil then x collect (list x y))
+ @result{} ((0 nil) (1 1) (2 2) (3 3) (4 4))
+(loop for x below 5 and y = nil then x collect (list x y))
+ @result{} ((0 nil) (1 0) (2 1) (3 2) (4 3))
address@hidden example
+
address@hidden
+In the first loop, @code{y} is set based on the value of @code{x}
+that was just set by the previous clause; in the second loop,
address@hidden and @code{y} are set simultaneously so @code{y} is set
+based on the value of @code{x} left over from the previous time
+through the loop.
+
+Another feature of the @code{loop} macro is @dfn{destructuring},
+similar in concept to the destructuring provided by @code{defmacro}.
+The @var{var} part of any @code{for} clause can be given as a list
+of variables instead of a single variable. The values produced
+during loop execution must be lists; the values in the lists are
+stored in the corresponding variables.
+
address@hidden
+(loop for (x y) in '((2 3) (4 5) (6 7)) collect (+ x y))
+ @result{} (5 9 13)
address@hidden example
+
+In loop destructuring, if there are more values than variables
+the trailing values are ignored, and if there are more variables
+than values the trailing variables get the value @code{nil}.
+If @code{nil} is used as a variable name, the corresponding
+values are ignored. Destructuring may be nested, and dotted
+lists of variables like @code{(x . y)} are allowed.
+
address@hidden Iteration Clauses, Accumulation Clauses, For Clauses, Loop
Facility
address@hidden Iteration Clauses
+
address@hidden
+Aside from @code{for} clauses, there are several other loop clauses
+that control the way the loop operates. They might be used by
+themselves, or in conjunction with one or more @code{for} clauses.
+
address@hidden @code
address@hidden repeat @var{integer}
+This clause simply counts up to the specified number using an
+internal temporary variable. The loops
+
address@hidden
+(loop repeat n do ...)
+(loop for temp to n do ...)
address@hidden example
+
address@hidden
+are identical except that the second one forces you to choose
+a name for a variable you aren't actually going to use.
+
address@hidden while @var{condition}
+This clause stops the loop when the specified condition (any Lisp
+expression) becomes @code{nil}. For example, the following two
+loops are equivalent, except for the implicit @code{nil} block
+that surrounds the second one:
+
address@hidden
+(while @var{cond} @address@hidden)
+(loop while @var{cond} do @address@hidden)
address@hidden example
+
address@hidden until @var{condition}
+This clause stops the loop when the specified condition is true,
+i.e., address@hidden
+
address@hidden always @var{condition}
+This clause stops the loop when the specified condition is @code{nil}.
+Unlike @code{while}, it stops the loop using @code{return nil} so that
+the @code{finally} clauses are not executed. If all the conditions
+were address@hidden, the loop returns @code{t}:
+
address@hidden
+(if (loop for size in size-list always (> size 10))
+ (some-big-sizes)
+ (no-big-sizes))
address@hidden example
+
address@hidden never @var{condition}
+This clause is like @code{always}, except that the loop returns
address@hidden if any conditions were false, or @code{nil} otherwise.
+
address@hidden thereis @var{condition}
+This clause stops the loop when the specified form is address@hidden;
+in this case, it returns that address@hidden value. If all the
+values were @code{nil}, the loop returns @code{nil}.
address@hidden table
+
address@hidden Accumulation Clauses, Other Clauses, Iteration Clauses, Loop
Facility
address@hidden Accumulation Clauses
+
address@hidden
+These clauses cause the loop to accumulate information about the
+specified Lisp @var{form}. The accumulated result is returned
+from the loop unless overridden, say, by a @code{return} clause.
+
address@hidden @code
address@hidden collect @var{form}
+This clause collects the values of @var{form} into a list. Several
+examples of @code{collect} appear elsewhere in this manual.
+
+The word @code{collecting} is a synonym for @code{collect}, and
+likewise for the other accumulation clauses.
+
address@hidden append @var{form}
+This clause collects lists of values into a result list using
address@hidden
+
address@hidden nconc @var{form}
+This clause collects lists of values into a result list by
+destructively modifying the lists rather than copying them.
+
address@hidden concat @var{form}
+This clause concatenates the values of the specified @var{form}
+into a string. (It and the following clause are extensions to
+standard Common Lisp.)
+
address@hidden vconcat @var{form}
+This clause concatenates the values of the specified @var{form}
+into a vector.
+
address@hidden count @var{form}
+This clause counts the number of times the specified @var{form}
+evaluates to a address@hidden value.
+
address@hidden sum @var{form}
+This clause accumulates the sum of the values of the specified
address@hidden, which must evaluate to a number.
+
address@hidden maximize @var{form}
+This clause accumulates the maximum value of the specified @var{form},
+which must evaluate to a number. The return value is undefined if
address@hidden is executed zero times.
+
address@hidden minimize @var{form}
+This clause accumulates the minimum value of the specified @var{form}.
address@hidden table
+
+Accumulation clauses can be followed by @samp{into @var{var}} to
+cause the data to be collected into variable @var{var} (which is
+automatically @code{let}-bound during the loop) rather than an
+unnamed temporary variable. Also, @code{into} accumulations do
+not automatically imply a return value. The loop must use some
+explicit mechanism, such as @code{finally return}, to return
+the accumulated result.
+
+It is valid for several accumulation clauses of the same type to
+accumulate into the same place. From Steele:
+
address@hidden
+(loop for name in '(fred sue alice joe june)
+ for kids in '((bob ken) () () (kris sunshine) ())
+ collect name
+ append kids)
+ @result{} (fred bob ken sue alice joe kris sunshine june)
address@hidden example
+
address@hidden Other Clauses, , Accumulation Clauses, Loop Facility
address@hidden Other Clauses
+
address@hidden
+This section describes the remaining loop clauses.
+
address@hidden @code
address@hidden with @var{var} = @var{value}
+This clause binds a variable to a value around the loop, but
+otherwise leaves the variable alone during the loop. The following
+loops are basically equivalent:
+
address@hidden
+(loop with x = 17 do ...)
+(let ((x 17)) (loop do ...))
+(loop for x = 17 then x do ...)
address@hidden example
+
+Naturally, the variable @var{var} might be used for some purpose
+in the rest of the loop. For example:
+
address@hidden
+(loop for x in my-list with res = nil do (push x res)
+ finally return res)
address@hidden example
+
+This loop inserts the elements of @code{my-list} at the front of
+a new list being accumulated in @code{res}, then returns the
+list @code{res} at the end of the loop. The effect is similar
+to that of a @code{collect} clause, but the list gets reversed
+by virtue of the fact that elements are being pushed onto the
+front of @code{res} rather than the end.
+
+If you omit the @code{=} term, the variable is initialized to
address@hidden (Thus the @samp{= nil} in the above example is
+unnecessary.)
+
+Bindings made by @code{with} are sequential by default, as if
+by @code{let*}. Just like @code{for} clauses, @code{with} clauses
+can be linked with @code{and} to cause the bindings to be made by
address@hidden instead.
+
address@hidden if @var{condition} @var{clause}
+This clause executes the following loop clause only if the specified
+condition is true. The following @var{clause} should be an accumulation,
address@hidden, @code{return}, @code{if}, or @code{unless} clause.
+Several clauses may be linked by separating them with @code{and}.
+These clauses may be followed by @code{else} and a clause or clauses
+to execute if the condition was false. The whole construct may
+optionally be followed by the word @code{end} (which may be used to
+disambiguate an @code{else} or @code{and} in a nested @code{if}).
+
+The actual address@hidden value of the condition form is available
+by the name @code{it} in the ``then'' part. For example:
+
address@hidden
+(setq funny-numbers '(6 13 -1))
+ @result{} (6 13 -1)
+(loop for x below 10
+ if (oddp x)
+ collect x into odds
+ and if (memq x funny-numbers) return (cdr it) end
+ else
+ collect x into evens
+ finally return (vector odds evens))
+ @result{} [(1 3 5 7 9) (0 2 4 6 8)]
+(setq funny-numbers '(6 7 13 -1))
+ @result{} (6 7 13 -1)
+(loop <@r{same thing again}>)
+ @result{} (13 -1)
address@hidden example
+
+Note the use of @code{and} to put two clauses into the ``then''
+part, one of which is itself an @code{if} clause. Note also that
address@hidden, while normally optional, was necessary here to make
+it clear that the @code{else} refers to the outermost @code{if}
+clause. In the first case, the loop returns a vector of lists
+of the odd and even values of @var{x}. In the second case, the
+odd number 7 is one of the @code{funny-numbers} so the loop
+returns early; the actual returned value is based on the result
+of the @code{memq} call.
+
address@hidden when @var{condition} @var{clause}
+This clause is just a synonym for @code{if}.
+
address@hidden unless @var{condition} @var{clause}
+The @code{unless} clause is just like @code{if} except that the
+sense of the condition is reversed.
+
address@hidden named @var{name}
+This clause gives a name other than @code{nil} to the implicit
+block surrounding the loop. The @var{name} is the symbol to be
+used as the block name.
+
address@hidden initially [do] @var{forms}...
+This keyword introduces one or more Lisp forms which will be
+executed before the loop itself begins (but after any variables
+requested by @code{for} or @code{with} have been bound to their
+initial values). @code{initially} clauses can appear anywhere;
+if there are several, they are executed in the order they appear
+in the loop. The keyword @code{do} is optional.
+
address@hidden finally [do] @var{forms}...
+This introduces Lisp forms which will be executed after the loop
+finishes (say, on request of a @code{for} or @code{while}).
address@hidden and @code{finally} clauses may appear anywhere
+in the loop construct, but they are executed (in the specified
+order) at the beginning or end, respectively, of the loop.
+
address@hidden finally return @var{form}
+This says that @var{form} should be executed after the loop
+is done to obtain a return value. (Without this, or some other
+clause like @code{collect} or @code{return}, the loop will simply
+return @code{nil}.) Variables bound by @code{for}, @code{with},
+or @code{into} will still contain their final values when @var{form}
+is executed.
+
address@hidden do @var{forms}...
+The word @code{do} may be followed by any number of Lisp expressions
+which are executed as an implicit @code{progn} in the body of the
+loop. Many of the examples in this section illustrate the use of
address@hidden
+
address@hidden return @var{form}
+This clause causes the loop to return immediately. The following
+Lisp form is evaluated to give the return value of the @code{loop}
+form. The @code{finally} clauses, if any, are not executed.
+Of course, @code{return} is generally used inside an @code{if} or
address@hidden, as its use in a top-level loop clause would mean
+the loop would never get to ``loop'' more than once.
+
+The clause @samp{return @var{form}} is equivalent to
address@hidden (return @var{form})} (or @code{return-from} if the loop
+was named). The @code{return} clause is implemented a bit more
+efficiently, though.
address@hidden table
+
+While there is no high-level way to add user extensions to @code{loop}
+(comparable to @code{defsetf} for @code{setf}, say), this package
+does offer two properties called @code{cl-loop-handler} and
address@hidden which are functions to be called when
+a given symbol is encountered as a top-level loop clause or
address@hidden clause, respectively. Consult the source code in
+file @file{cl-macs.el} for details.
+
+This package's @code{loop} macro is compatible with that of Common
+Lisp, except that a few features are not implemented: @code{loop-finish}
+and data-type specifiers. Naturally, the @code{for} clauses which
+iterate over keymaps, overlays, intervals, frames, windows, and
+buffers are Emacs-specific extensions.
+
address@hidden Multiple Values, , Loop Facility, Control Structure
address@hidden Multiple Values
+
address@hidden
+Common Lisp functions can return zero or more results. Emacs Lisp
+functions, by contrast, always return exactly one result. This
+package makes no attempt to emulate Common Lisp multiple return
+values; Emacs versions of Common Lisp functions that return more
+than one value either return just the first value (as in
address@hidden) or return a list of values (as in
address@hidden). This package @emph{does} define placeholders
+for the Common Lisp functions that work with multiple values, but
+in Emacs Lisp these functions simply operate on lists instead.
+The @code{values} form, for example, is a synonym for @code{list}
+in Emacs.
+
address@hidden multiple-value-bind (address@hidden) values-form address@hidden
+This form evaluates @var{values-form}, which must return a list of
+values. It then binds the @var{var}s to these respective values,
+as if by @code{let}, and then executes the body @var{forms}.
+If there are more @var{var}s than values, the extra @var{var}s
+are bound to @code{nil}. If there are fewer @var{var}s than
+values, the excess values are ignored.
address@hidden defspec
+
address@hidden multiple-value-setq (address@hidden) form
+This form evaluates @var{form}, which must return a list of values.
+It then sets the @var{var}s to these respective values, as if by
address@hidden Extra @var{var}s or values are treated the same as
+in @code{multiple-value-bind}.
address@hidden defspec
+
+The older Quiroz package attempted a more faithful (but still
+imperfect) emulation of Common Lisp multiple values. The old
+method ``usually'' simulated true multiple values quite well,
+but under certain circumstances would leave spurious return
+values in memory where a later, unrelated @code{multiple-value-bind}
+form would see them.
+
+Since a perfect emulation is not feasible in Emacs Lisp, this
+package opts to keep it as simple and predictable as possible.
+
address@hidden Macros, Declarations, Control Structure, Top
address@hidden Macros
+
address@hidden
+This package implements the various Common Lisp features of
address@hidden, such as destructuring, @code{&environment},
+and @code{&body}. Top-level @code{&whole} is not implemented
+for @code{defmacro} due to technical difficulties.
address@hidden Lists}.
+
+Destructuring is made available to the user by way of the
+following macro:
+
address@hidden destructuring-bind arglist expr address@hidden
+This macro expands to code which executes @var{forms}, with
+the variables in @var{arglist} bound to the list of values
+returned by @var{expr}. The @var{arglist} can include all
+the features allowed for @code{defmacro} argument lists,
+including destructuring. (The @code{&environment} keyword
+is not allowed.) The macro expansion will signal an error
+if @var{expr} returns a list of the wrong number of arguments
+or with incorrect keyword arguments.
address@hidden defspec
+
+This package also includes the Common Lisp @code{define-compiler-macro}
+facility, which allows you to define compile-time expansions and
+optimizations for your functions.
+
address@hidden define-compiler-macro name arglist address@hidden
+This form is similar to @code{defmacro}, except that it only expands
+calls to @var{name} at compile-time; calls processed by the Lisp
+interpreter are not expanded, nor are they expanded by the
address@hidden function.
+
+The argument list may begin with a @code{&whole} keyword and a
+variable. This variable is bound to the macro-call form itself,
+i.e., to a list of the form @samp{(@var{name} @address@hidden)}.
+If the macro expander returns this form unchanged, then the
+compiler treats it as a normal function call. This allows
+compiler macros to work as optimizers for special cases of a
+function, leaving complicated cases alone.
+
+For example, here is a simplified version of a definition that
+appears as a standard part of this package:
+
address@hidden
+(define-compiler-macro member* (&whole form a list &rest keys)
+ (if (and (null keys)
+ (eq (car-safe a) 'quote)
+ (not (floatp-safe (cadr a))))
+ (list 'memq a list)
+ form))
address@hidden example
+
address@hidden
+This definition causes @code{(member* @var{a} @var{list})} to change
+to a call to the faster @code{memq} in the common case where @var{a}
+is a non-floating-point constant; if @var{a} is anything else, or
+if there are any keyword arguments in the call, then the original
address@hidden call is left intact. (The actual compiler macro
+for @code{member*} optimizes a number of other cases, including
+common @code{:test} predicates.)
address@hidden defspec
+
address@hidden compiler-macroexpand form
+This function is analogous to @code{macroexpand}, except that it
+expands compiler macros rather than regular macros. It returns
address@hidden unchanged if it is not a call to a function for which
+a compiler macro has been defined, or if that compiler macro
+decided to punt by returning its @code{&whole} argument. Like
address@hidden, it expands repeatedly until it reaches a form
+for which no further expansion is possible.
address@hidden defun
+
address@hidden Bindings}, for descriptions of the @code{macrolet}
+and @code{symbol-macrolet} forms for making ``local'' macro
+definitions.
+
address@hidden Declarations, Symbols, Macros, Top
address@hidden Declarations
+
address@hidden
+Common Lisp includes a complex and powerful ``declaration''
+mechanism that allows you to give the compiler special hints
+about the types of data that will be stored in particular variables,
+and about the ways those variables and functions will be used. This
+package defines versions of all the Common Lisp declaration forms:
address@hidden, @code{locally}, @code{proclaim}, @code{declaim},
+and @code{the}.
+
+Most of the Common Lisp declarations are not currently useful in
+Emacs Lisp, as the byte-code system provides little opportunity
+to benefit from type information, and @code{special} declarations
+are redundant in a fully dynamically-scoped Lisp. A few
+declarations are meaningful when the optimizing byte
+compiler is being used, however. Under the earlier non-optimizing
+compiler, these declarations will effectively be ignored.
+
address@hidden proclaim decl-spec
+This function records a ``global'' declaration specified by
address@hidden Since @code{proclaim} is a function, @var{decl-spec}
+is evaluated and thus should normally be quoted.
address@hidden defun
+
address@hidden declaim address@hidden
+This macro is like @code{proclaim}, except that it takes any number
+of @var{decl-spec} arguments, and the arguments are unevaluated and
+unquoted. The @code{declaim} macro also puts an @code{(eval-when
+(compile load eval) ...)} around the declarations so that they will
+be registered at compile-time as well as at run-time. (This is vital,
+since normally the declarations are meant to influence the way the
+compiler treats the rest of the file that contains the @code{declaim}
+form.)
address@hidden defspec
+
address@hidden declare address@hidden
+This macro is used to make declarations within functions and other
+code. Common Lisp allows declarations in various locations, generally
+at the beginning of any of the many ``implicit @code{progn}s''
+throughout Lisp syntax, such as function bodies, @code{let} bodies,
+etc. Currently the only declaration understood by @code{declare}
+is @code{special}.
address@hidden defspec
+
address@hidden locally address@hidden address@hidden
+In this package, @code{locally} is no different from @code{progn}.
address@hidden defspec
+
address@hidden the type form
+Type information provided by @code{the} is ignored in this package;
+in other words, @code{(the @var{type} @var{form})} is equivalent
+to @var{form}. Future versions of the optimizing byte-compiler may
+make use of this information.
+
+For example, @code{mapcar} can map over both lists and arrays. It is
+hard for the compiler to expand @code{mapcar} into an in-line loop
+unless it knows whether the sequence will be a list or an array ahead
+of time. With @code{(mapcar 'car (the vector foo))}, a future
+compiler would have enough information to expand the loop in-line.
+For now, Emacs Lisp will treat the above code as exactly equivalent
+to @code{(mapcar 'car foo)}.
address@hidden defspec
+
+Each @var{decl-spec} in a @code{proclaim}, @code{declaim}, or
address@hidden should be a list beginning with a symbol that says
+what kind of declaration it is. This package currently understands
address@hidden, @code{inline}, @code{notinline}, @code{optimize},
+and @code{warn} declarations. (The @code{warn} declaration is an
+extension of standard Common Lisp.) Other Common Lisp declarations,
+such as @code{type} and @code{ftype}, are silently ignored.
+
address@hidden @code
address@hidden special
+Since all variables in Emacs Lisp are ``special'' (in the Common
+Lisp sense), @code{special} declarations are only advisory. They
+simply tell the optimizing byte compiler that the specified
+variables are intentionally being referred to without being
+bound in the body of the function. The compiler normally emits
+warnings for such references, since they could be typographical
+errors for references to local variables.
+
+The declaration @code{(declare (special @var{var1} @var{var2}))} is
+equivalent to @code{(defvar @var{var1}) (defvar @var{var2})} in the
+optimizing compiler, or to nothing at all in older compilers (which
+do not warn for non-local references).
+
+In top-level contexts, it is generally better to write
address@hidden(defvar @var{var})} than @code{(declaim (special @var{var}))},
+since @code{defvar} makes your intentions clearer. But the older
+byte compilers can not handle @code{defvar}s appearing inside of
+functions, while @code{(declare (special @var{var}))} takes care
+to work correctly with all compilers.
+
address@hidden inline
+The @code{inline} @var{decl-spec} lists one or more functions
+whose bodies should be expanded ``in-line'' into calling functions
+whenever the compiler is able to arrange for it. For example,
+the Common Lisp function @code{cadr} is declared @code{inline}
+by this package so that the form @code{(cadr @var{x})} will
+expand directly into @code{(car (cdr @var{x}))} when it is called
+in user functions, for a savings of one (relatively expensive)
+function call.
+
+The following declarations are all equivalent. Note that the
address@hidden form is a convenient way to define a function
+and declare it inline all at once.
+
address@hidden
+(declaim (inline foo bar))
+(eval-when (compile load eval) (proclaim '(inline foo bar)))
+(defsubst foo (...) ...) ; instead of defun
address@hidden example
+
address@hidden note:} this declaration remains in effect after the
+containing source file is done. It is correct to use it to
+request that a function you have defined should be inlined,
+but it is impolite to use it to request inlining of an external
+function.
+
+In Common Lisp, it is possible to use @code{(declare (inline @dots{}))}
+before a particular call to a function to cause just that call to
+be inlined; the current byte compilers provide no way to implement
+this, so @code{(declare (inline @dots{}))} is currently ignored by
+this package.
+
address@hidden notinline
+The @code{notinline} declaration lists functions which should
+not be inlined after all; it cancels a previous @code{inline}
+declaration.
+
address@hidden optimize
+This declaration controls how much optimization is performed by
+the compiler. Naturally, it is ignored by the earlier non-optimizing
+compilers.
+
+The word @code{optimize} is followed by any number of lists like
address@hidden(speed 3)} or @code{(safety 2)}. Common Lisp defines several
+optimization ``qualities''; this package ignores all but @code{speed}
+and @code{safety}. The value of a quality should be an integer from
+0 to 3, with 0 meaning ``unimportant'' and 3 meaning ``very important.''
+The default level for both qualities is 1.
+
+In this package, with the optimizing compiler, the
address@hidden quality is tied to the @code{byte-compile-optimize}
+flag, which is set to @code{nil} for @code{(speed 0)} and to
address@hidden for higher settings; and the @code{safety} quality is
+tied to the @code{byte-compile-delete-errors} flag, which is
+set to @code{t} for @code{(safety 3)} and to @code{nil} for all
+lower settings. (The latter flag controls whether the compiler
+is allowed to optimize out code whose only side-effect could
+be to signal an error, e.g., rewriting @code{(progn foo bar)} to
address@hidden when it is not known whether @code{foo} will be bound
+at run-time.)
+
+Note that even compiling with @code{(safety 0)}, the Emacs
+byte-code system provides sufficient checking to prevent real
+harm from being done. For example, barring serious bugs in
+Emacs itself, Emacs will not crash with a segmentation fault
+just because of an error in a fully-optimized Lisp program.
+
+The @code{optimize} declaration is normally used in a top-level
address@hidden or @code{declaim} in a file; Common Lisp allows
+it to be used with @code{declare} to set the level of optimization
+locally for a given form, but this will not work correctly with the
+current version of the optimizing compiler. (The @code{declare}
+will set the new optimization level, but that level will not
+automatically be unset after the enclosing form is done.)
+
address@hidden warn
+This declaration controls what sorts of warnings are generated
+by the byte compiler. Again, only the optimizing compiler
+generates warnings. The word @code{warn} is followed by any
+number of ``warning qualities,'' similar in form to optimization
+qualities. The currently supported warning types are
address@hidden, @code{callargs}, @code{unresolved}, and
address@hidden; in the current system, a value of 0 will
+disable these warnings and any higher value will enable them.
+See the documentation for the optimizing byte compiler for details.
address@hidden table
+
address@hidden Symbols, Numbers, Declarations, Top
address@hidden Symbols
+
address@hidden
+This package defines several symbol-related features that were
+missing from Emacs Lisp.
+
address@hidden
+* Property Lists:: `get*', `remprop', `getf', `remf'
+* Creating Symbols:: `gensym', `gentemp'
address@hidden menu
+
address@hidden Property Lists, Creating Symbols, Symbols, Symbols
address@hidden Property Lists
+
address@hidden
+These functions augment the standard Emacs Lisp functions @code{get}
+and @code{put} for operating on properties attached to symbols.
+There are also functions for working with property lists as
+first-class data structures not attached to particular symbols.
+
address@hidden get* symbol property &optional default
+This function is like @code{get}, except that if the property is
+not found, the @var{default} argument provides the return value.
+(The Emacs Lisp @code{get} function always uses @code{nil} as
+the default; this package's @code{get*} is equivalent to Common
+Lisp's @code{get}.)
+
+The @code{get*} function is @code{setf}-able; when used in this
+fashion, the @var{default} argument is allowed but ignored.
address@hidden defun
+
address@hidden remprop symbol property
+This function removes the entry for @var{property} from the property
+list of @var{symbol}. It returns a true value if the property was
+indeed found and removed, or @code{nil} if there was no such property.
+(This function was probably omitted from Emacs originally because,
+since @code{get} did not allow a @var{default}, it was very difficult
+to distinguish between a missing property and a property whose value
+was @code{nil}; thus, setting a property to @code{nil} was close
+enough to @code{remprop} for most purposes.)
address@hidden defun
+
address@hidden getf place property &optional default
+This function scans the list @var{place} as if it were a property
+list, i.e., a list of alternating property names and values. If
+an even-numbered element of @var{place} is found which is @code{eq}
+to @var{property}, the following odd-numbered element is returned.
+Otherwise, @var{default} is returned (or @code{nil} if no default
+is given).
+
+In particular,
+
address@hidden
+(get sym prop) @equiv{} (getf (symbol-plist sym) prop)
address@hidden example
+
+It is valid to use @code{getf} as a @code{setf} place, in which case
+its @var{place} argument must itself be a valid @code{setf} place.
+The @var{default} argument, if any, is ignored in this context.
+The effect is to change (via @code{setcar}) the value cell in the
+list that corresponds to @var{property}, or to cons a new property-value
+pair onto the list if the property is not yet present.
+
address@hidden
+(put sym prop val) @equiv{} (setf (getf (symbol-plist sym) prop) val)
address@hidden example
+
+The @code{get} and @code{get*} functions are also @code{setf}-able.
+The fact that @code{default} is ignored can sometimes be useful:
+
address@hidden
+(incf (get* 'foo 'usage-count 0))
address@hidden example
+
+Here, symbol @code{foo}'s @code{usage-count} property is incremented
+if it exists, or set to 1 (an incremented 0) otherwise.
+
+When not used as a @code{setf} form, @code{getf} is just a regular
+function and its @var{place} argument can actually be any Lisp
+expression.
address@hidden defun
+
address@hidden remf place property
+This macro removes the property-value pair for @var{property} from
+the property list stored at @var{place}, which is any @code{setf}-able
+place expression. It returns true if the property was found. Note
+that if @var{property} happens to be first on the list, this will
+effectively do a @code{(setf @var{place} (cddr @var{place}))},
+whereas if it occurs later, this simply uses @code{setcdr} to splice
+out the property and value cells.
address@hidden defspec
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Creating Symbols, , Property Lists, Symbols
address@hidden Creating Symbols
+
address@hidden
+These functions create unique symbols, typically for use as
+temporary variables.
+
address@hidden gensym &optional x
+This function creates a new, uninterned symbol (using @code{make-symbol})
+with a unique name. (The name of an uninterned symbol is relevant
+only if the symbol is printed.) By default, the name is generated
+from an increasing sequence of numbers, @samp{G1000}, @samp{G1001},
address@hidden, etc. If the optional argument @var{x} is a string, that
+string is used as a prefix instead of @samp{G}. Uninterned symbols
+are used in macro expansions for temporary variables, to ensure that
+their names will not conflict with ``real'' variables in the user's
+code.
address@hidden defun
+
address@hidden *gensym-counter*
+This variable holds the counter used to generate @code{gensym} names.
+It is incremented after each use by @code{gensym}. In Common Lisp
+this is initialized with 0, but this package initializes it with a
+random (time-dependent) value to avoid trouble when two files that
+each used @code{gensym} in their compilation are loaded together.
+(Uninterned symbols become interned when the compiler writes them
+out to a file and the Emacs loader loads them, so their names have to
+be treated a bit more carefully than in Common Lisp where uninterned
+symbols remain uninterned after loading.)
address@hidden defvar
+
address@hidden gentemp &optional x
+This function is like @code{gensym}, except that it produces a new
address@hidden symbol. If the symbol that is generated already
+exists, the function keeps incrementing the counter and trying
+again until a new symbol is generated.
address@hidden defun
+
+The Quiroz @file{cl.el} package also defined a @code{defkeyword}
+form for creating self-quoting keyword symbols. This package
+automatically creates all keywords that are called for by
address@hidden&key} argument specifiers, and discourages the use of
+keywords as data unrelated to keyword arguments, so the
address@hidden form has been discontinued.
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Numbers, Sequences, Symbols, Top
address@hidden Numbers
+
address@hidden
+This section defines a few simple Common Lisp operations on numbers
+which were left out of Emacs Lisp.
+
address@hidden
+* Predicates on Numbers:: `plusp', `oddp', `floatp-safe', etc.
+* Numerical Functions:: `abs', `floor*', etc.
+* Random Numbers:: `random*', `make-random-state'
+* Implementation Parameters:: `most-positive-float'
address@hidden menu
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Predicates on Numbers, Numerical Functions, Numbers, Numbers
address@hidden Predicates on Numbers
+
address@hidden
+These functions return @code{t} if the specified condition is
+true of the numerical argument, or @code{nil} otherwise.
+
address@hidden plusp number
+This predicate tests whether @var{number} is positive. It is an
+error if the argument is not a number.
address@hidden defun
+
address@hidden minusp number
+This predicate tests whether @var{number} is negative. It is an
+error if the argument is not a number.
address@hidden defun
+
address@hidden oddp integer
+This predicate tests whether @var{integer} is odd. It is an
+error if the argument is not an integer.
address@hidden defun
+
address@hidden evenp integer
+This predicate tests whether @var{integer} is even. It is an
+error if the argument is not an integer.
address@hidden defun
+
address@hidden floatp-safe object
+This predicate tests whether @var{object} is a floating-point
+number. On systems that support floating-point, this is equivalent
+to @code{floatp}. On other systems, this always returns @code{nil}.
address@hidden defun
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Numerical Functions, Random Numbers, Predicates on Numbers,
Numbers
address@hidden Numerical Functions
+
address@hidden
+These functions perform various arithmetic operations on numbers.
+
address@hidden gcd &rest integers
+This function returns the Greatest Common Divisor of the arguments.
+For one argument, it returns the absolute value of that argument.
+For zero arguments, it returns zero.
address@hidden defun
+
address@hidden lcm &rest integers
+This function returns the Least Common Multiple of the arguments.
+For one argument, it returns the absolute value of that argument.
+For zero arguments, it returns one.
address@hidden defun
+
address@hidden isqrt integer
+This function computes the ``integer square root'' of its integer
+argument, i.e., the greatest integer less than or equal to the true
+square root of the argument.
address@hidden defun
+
address@hidden floor* number &optional divisor
+This function implements the Common Lisp @code{floor} function.
+It is called @code{floor*} to avoid name conflicts with the
+simpler @code{floor} function built-in to Emacs.
+
+With one argument, @code{floor*} returns a list of two numbers:
+The argument rounded down (toward minus infinity) to an integer,
+and the ``remainder'' which would have to be added back to the
+first return value to yield the argument again. If the argument
+is an integer @var{x}, the result is always the list @code{(@var{x} 0)}.
+If the argument is a floating-point number, the first
+result is a Lisp integer and the second is a Lisp float between
+0 (inclusive) and 1 (exclusive).
+
+With two arguments, @code{floor*} divides @var{number} by
address@hidden, and returns the floor of the quotient and the
+corresponding remainder as a list of two numbers. If
address@hidden(floor* @var{x} @var{y})} returns @code{(@var{q} @var{r})},
+then @address@hidden@var{y} + @var{r} = @var{x}}, with @var{r}
+between 0 (inclusive) and @var{r} (exclusive). Also, note
+that @code{(floor* @var{x})} is exactly equivalent to
address@hidden(floor* @var{x} 1)}.
+
+This function is entirely compatible with Common Lisp's @code{floor}
+function, except that it returns the two results in a list since
+Emacs Lisp does not support multiple-valued functions.
address@hidden defun
+
address@hidden ceiling* number &optional divisor
+This function implements the Common Lisp @code{ceiling} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments up toward plus infinity.
+The remainder will be between 0 and minus @var{r}.
address@hidden defun
+
address@hidden truncate* number &optional divisor
+This function implements the Common Lisp @code{truncate} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments toward zero. Thus it is
+equivalent to @code{floor*} if the argument or quotient is
+positive, or to @code{ceiling*} otherwise. The remainder has
+the same sign as @var{number}.
address@hidden defun
+
address@hidden round* number &optional divisor
+This function implements the Common Lisp @code{round} function,
+which is analogous to @code{floor} except that it rounds the
+argument or quotient of the arguments to the nearest integer.
+In the case of a tie (the argument or quotient is exactly
+halfway between two integers), it rounds to the even integer.
address@hidden defun
+
address@hidden mod* number divisor
+This function returns the same value as the second return value
+of @code{floor}.
address@hidden defun
+
address@hidden rem* number divisor
+This function returns the same value as the second return value
+of @code{truncate}.
address@hidden defun
+
+These definitions are compatible with those in the Quiroz
address@hidden package, except that this package appends @samp{*}
+to certain function names to avoid conflicts with existing
+Emacs functions, and that the mechanism for returning
+multiple values is different.
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Random Numbers, Implementation Parameters, Numerical Functions,
Numbers
address@hidden Random Numbers
+
address@hidden
+This package also provides an implementation of the Common Lisp
+random number generator. It uses its own additive-congruential
+algorithm, which is much more likely to give statistically clean
+random numbers than the simple generators supplied by many
+operating systems.
+
address@hidden random* number &optional state
+This function returns a random nonnegative number less than
address@hidden, and of the same type (either integer or floating-point).
+The @var{state} argument should be a @code{random-state} object
+which holds the state of the random number generator. The
+function modifies this state object as a side effect. If
address@hidden is omitted, it defaults to the variable
address@hidden, which contains a pre-initialized
address@hidden object.
address@hidden defun
+
address@hidden *random-state*
+This variable contains the system ``default'' @code{random-state}
+object, used for calls to @code{random*} that do not specify an
+alternative state object. Since any number of programs in the
+Emacs process may be accessing @code{*random-state*} in interleaved
+fashion, the sequence generated from this variable will be
+irreproducible for all intents and purposes.
address@hidden defvar
+
address@hidden make-random-state &optional state
+This function creates or copies a @code{random-state} object.
+If @var{state} is omitted or @code{nil}, it returns a new copy of
address@hidden This is a copy in the sense that future
+sequences of calls to @code{(random* @var{n})} and
address@hidden(random* @var{n} @var{s})} (where @var{s} is the new
+random-state object) will return identical sequences of random
+numbers.
+
+If @var{state} is a @code{random-state} object, this function
+returns a copy of that object. If @var{state} is @code{t}, this
+function returns a new @code{random-state} object seeded from the
+date and time. As an extension to Common Lisp, @var{state} may also
+be an integer in which case the new object is seeded from that
+integer; each different integer seed will result in a completely
+different sequence of random numbers.
+
+It is valid to print a @code{random-state} object to a buffer or
+file and later read it back with @code{read}. If a program wishes
+to use a sequence of pseudo-random numbers which can be reproduced
+later for debugging, it can call @code{(make-random-state t)} to
+get a new sequence, then print this sequence to a file. When the
+program is later rerun, it can read the original run's random-state
+from the file.
address@hidden defun
+
address@hidden random-state-p object
+This predicate returns @code{t} if @var{object} is a
address@hidden object, or @code{nil} otherwise.
address@hidden defun
+
address@hidden Implementation Parameters, , Random Numbers, Numbers
address@hidden Implementation Parameters
+
address@hidden
+This package defines several useful constants having to with numbers.
+
+The following parameters have to do with floating-point numbers.
+This package determines their values by exercising the computer's
+floating-point arithmetic in various ways. Because this operation
+might be slow, the code for initializing them is kept in a separate
+function that must be called before the parameters can be used.
+
address@hidden cl-float-limits
+This function makes sure that the Common Lisp floating-point parameters
+like @code{most-positive-float} have been initialized. Until it is
+called, these parameters will be @code{nil}. If this version of Emacs
+does not support floats, the parameters will remain @code{nil}. If the
+parameters have already been initialized, the function returns
+immediately.
+
+The algorithm makes assumptions that will be valid for most modern
+machines, but will fail if the machine's arithmetic is extremely
+unusual, e.g., decimal.
address@hidden defun
+
+Since true Common Lisp supports up to four different floating-point
+precisions, it has families of constants like
address@hidden, @code{most-positive-double-float},
address@hidden, and so on. Emacs has only one
+floating-point precision, so this package omits the precision word
+from the constants' names.
+
address@hidden most-positive-float
+This constant equals the largest value a Lisp float can hold.
+For those systems whose arithmetic supports infinities, this is
+the largest @emph{finite} value. For IEEE machines, the value
+is approximately @code{1.79e+308}.
address@hidden defvar
+
address@hidden most-negative-float
+This constant equals the most-negative value a Lisp float can hold.
+(It is assumed to be equal to @code{(- most-positive-float)}.)
address@hidden defvar
+
address@hidden least-positive-float
+This constant equals the smallest Lisp float value greater than zero.
+For IEEE machines, it is about @code{4.94e-324} if denormals are
+supported or @code{2.22e-308} if not.
address@hidden defvar
+
address@hidden least-positive-normalized-float
+This constant equals the smallest @emph{normalized} Lisp float greater
+than zero, i.e., the smallest value for which IEEE denormalization
+will not result in a loss of precision. For IEEE machines, this
+value is about @code{2.22e-308}. For machines that do not support
+the concept of denormalization and gradual underflow, this constant
+will always equal @code{least-positive-float}.
address@hidden defvar
+
address@hidden least-negative-float
+This constant is the negative counterpart of @code{least-positive-float}.
address@hidden defvar
+
address@hidden least-negative-normalized-float
+This constant is the negative counterpart of
address@hidden
address@hidden defvar
+
address@hidden float-epsilon
+This constant is the smallest positive Lisp float that can be added
+to 1.0 to produce a distinct value. Adding a smaller number to 1.0
+will yield 1.0 again due to roundoff. For IEEE machines, epsilon
+is about @code{2.22e-16}.
address@hidden defvar
+
address@hidden float-negative-epsilon
+This is the smallest positive value that can be subtracted from
+1.0 to produce a distinct value. For IEEE machines, it is about
address@hidden
address@hidden defvar
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Sequences, Lists, Numbers, Top
address@hidden Sequences
+
address@hidden
+Common Lisp defines a number of functions that operate on
address@hidden, which are either lists, strings, or vectors.
+Emacs Lisp includes a few of these, notably @code{elt} and
address@hidden; this package defines most of the rest.
+
address@hidden
+* Sequence Basics:: Arguments shared by all sequence functions
+* Mapping over Sequences:: `mapcar*', `mapcan', `map', `every', etc.
+* Sequence Functions:: `subseq', `remove*', `substitute', etc.
+* Searching Sequences:: `find', `position', `count', `search', etc.
+* Sorting Sequences:: `sort*', `stable-sort', `merge'
address@hidden menu
+
address@hidden Sequence Basics, Mapping over Sequences, Sequences, Sequences
address@hidden Sequence Basics
+
address@hidden
+Many of the sequence functions take keyword arguments; @pxref{Argument
+Lists}. All keyword arguments are optional and, if specified,
+may appear in any order.
+
+The @code{:key} argument should be passed either @code{nil}, or a
+function of one argument. This key function is used as a filter
+through which the elements of the sequence are seen; for example,
address@hidden(find x y :key 'car)} is similar to @code{(assoc* x y)}:
+It searches for an element of the list whose @code{car} equals
address@hidden, rather than for an element which equals @code{x} itself.
+If @code{:key} is omitted or @code{nil}, the filter is effectively
+the identity function.
+
+The @code{:test} and @code{:test-not} arguments should be either
address@hidden, or functions of two arguments. The test function is
+used to compare two sequence elements, or to compare a search value
+with sequence elements. (The two values are passed to the test
+function in the same order as the original sequence function
+arguments from which they are derived, or, if they both come from
+the same sequence, in the same order as they appear in that sequence.)
+The @code{:test} argument specifies a function which must return
+true (address@hidden) to indicate a match; instead, you may use
address@hidden:test-not} to give a function which returns @emph{false} to
+indicate a match. The default test function is @code{:test 'eql}.
+
+Many functions which take @var{item} and @code{:test} or @code{:test-not}
+arguments also come in @code{-if} and @code{-if-not} varieties,
+where a @var{predicate} function is passed instead of @var{item},
+and sequence elements match if the predicate returns true on them
+(or false in the case of @code{-if-not}). For example:
+
address@hidden
+(remove* 0 seq :test '=) @equiv{} (remove-if 'zerop seq)
address@hidden example
+
address@hidden
+to remove all zeros from sequence @code{seq}.
+
+Some operations can work on a subsequence of the argument sequence;
+these function take @code{:start} and @code{:end} arguments which
+default to zero and the length of the sequence, respectively.
+Only elements between @var{start} (inclusive) and @var{end}
+(exclusive) are affected by the operation. The @var{end} argument
+may be passed @code{nil} to signify the length of the sequence;
+otherwise, both @var{start} and @var{end} must be integers, with
address@hidden <= @var{start} <= @var{end} <= (length @var{seq})}.
+If the function takes two sequence arguments, the limits are
+defined by keywords @code{:start1} and @code{:end1} for the first,
+and @code{:start2} and @code{:end2} for the second.
+
+A few functions accept a @code{:from-end} argument, which, if
address@hidden, causes the operation to go from right-to-left
+through the sequence instead of left-to-right, and a @code{:count}
+argument, which specifies an integer maximum number of elements
+to be removed or otherwise processed.
+
+The sequence functions make no guarantees about the order in
+which the @code{:test}, @code{:test-not}, and @code{:key} functions
+are called on various elements. Therefore, it is a bad idea to depend
+on side effects of these functions. For example, @code{:from-end}
+may cause the sequence to be scanned actually in reverse, or it may
+be scanned forwards but computing a result ``as if'' it were scanned
+backwards. (Some functions, like @code{mapcar*} and @code{every},
address@hidden specify exactly the order in which the function is called
+so side effects are perfectly acceptable in those cases.)
+
+Strings may contain ``text properties'' as well
+as character data. Except as noted, it is undefined whether or
+not text properties are preserved by sequence functions. For
+example, @code{(remove* ?A @var{str})} may or may not preserve
+the properties of the characters copied from @var{str} into the
+result.
+
address@hidden Mapping over Sequences, Sequence Functions, Sequence Basics,
Sequences
address@hidden Mapping over Sequences
+
address@hidden
+These functions ``map'' the function you specify over the elements
+of lists or arrays. They are all variations on the theme of the
+built-in function @code{mapcar}.
+
address@hidden mapcar* function seq &rest more-seqs
+This function calls @var{function} on successive parallel sets of
+elements from its argument sequences. Given a single @var{seq}
+argument it is equivalent to @code{mapcar}; given @var{n} sequences,
+it calls the function with the first elements of each of the sequences
+as the @var{n} arguments to yield the first element of the result
+list, then with the second elements, and so on. The mapping stops as
+soon as the shortest sequence runs out. The argument sequences may
+be any mixture of lists, strings, and vectors; the return sequence
+is always a list.
+
+Common Lisp's @code{mapcar} accepts multiple arguments but works
+only on lists; Emacs Lisp's @code{mapcar} accepts a single sequence
+argument. This package's @code{mapcar*} works as a compatible
+superset of both.
address@hidden defun
+
address@hidden map result-type function seq &rest more-seqs
+This function maps @var{function} over the argument sequences,
+just like @code{mapcar*}, but it returns a sequence of type
address@hidden rather than a list. @var{result-type} must
+be one of the following symbols: @code{vector}, @code{string},
address@hidden (in which case the effect is the same as for
address@hidden), or @code{nil} (in which case the results are
+thrown away and @code{map} returns @code{nil}).
address@hidden defun
+
address@hidden maplist function list &rest more-lists
+This function calls @var{function} on each of its argument lists,
+then on the @code{cdr}s of those lists, and so on, until the
+shortest list runs out. The results are returned in the form
+of a list. Thus, @code{maplist} is like @code{mapcar*} except
+that it passes in the list pointers themselves rather than the
address@hidden of the advancing pointers.
address@hidden defun
+
address@hidden mapc function seq &rest more-seqs
+This function is like @code{mapcar*}, except that the values returned
+by @var{function} are ignored and thrown away rather than being
+collected into a list. The return value of @code{mapc} is @var{seq},
+the first sequence. This function is more general than the Emacs
+primitive @code{mapc}.
address@hidden defun
+
address@hidden mapl function list &rest more-lists
+This function is like @code{maplist}, except that it throws away
+the values returned by @var{function}.
address@hidden defun
+
address@hidden mapcan function seq &rest more-seqs
+This function is like @code{mapcar*}, except that it concatenates
+the return values (which must be lists) using @code{nconc},
+rather than simply collecting them into a list.
address@hidden defun
+
address@hidden mapcon function list &rest more-lists
+This function is like @code{maplist}, except that it concatenates
+the return values using @code{nconc}.
address@hidden defun
+
address@hidden some predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of @var{seq}
+in turn; if @var{predicate} returns a address@hidden value,
address@hidden returns that value, otherwise it returns @code{nil}.
+Given several sequence arguments, it steps through the sequences
+in parallel until the shortest one runs out, just as in
address@hidden You can rely on the left-to-right order in which
+the elements are visited, and on the fact that mapping stops
+immediately as soon as @var{predicate} returns address@hidden
address@hidden defun
+
address@hidden every predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns @code{nil} as soon as @var{predicate} returns
address@hidden for any element, or @code{t} if the predicate was true
+for all elements.
address@hidden defun
+
address@hidden notany predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns @code{nil} as soon as @var{predicate} returns
+a address@hidden value for any element, or @code{t} if the predicate
+was @code{nil} for all elements.
address@hidden defun
+
address@hidden notevery predicate seq &rest more-seqs
+This function calls @var{predicate} on each element of the sequence(s)
+in turn; it returns a address@hidden value as soon as @var{predicate}
+returns @code{nil} for any element, or @code{t} if the predicate was
+true for all elements.
address@hidden defun
+
address@hidden reduce function seq @t{&key :from-end :start :end :initial-value
:key}
+This function combines the elements of @var{seq} using an associative
+binary operation. Suppose @var{function} is @code{*} and @var{seq} is
+the list @code{(2 3 4 5)}. The first two elements of the list are
+combined with @code{(* 2 3) = 6}; this is combined with the next
+element, @code{(* 6 4) = 24}, and that is combined with the final
+element: @code{(* 24 5) = 120}. Note that the @code{*} function happens
+to be self-reducing, so that @code{(* 2 3 4 5)} has the same effect as
+an explicit call to @code{reduce}.
+
+If @code{:from-end} is true, the reduction is right-associative instead
+of left-associative:
+
address@hidden
+(reduce '- '(1 2 3 4))
+ @equiv{} (- (- (- 1 2) 3) 4) @result{} -8
+(reduce '- '(1 2 3 4) :from-end t)
+ @equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
address@hidden example
+
+If @code{:key} is specified, it is a function of one argument which
+is called on each of the sequence elements in turn.
+
+If @code{:initial-value} is specified, it is effectively added to the
+front (or rear in the case of @code{:from-end}) of the sequence.
+The @code{:key} function is @emph{not} applied to the initial value.
+
+If the sequence, including the initial value, has exactly one element
+then that element is returned without ever calling @var{function}.
+If the sequence is empty (and there is no initial value), then
address@hidden is called with no arguments to obtain the return value.
address@hidden defun
+
+All of these mapping operations can be expressed conveniently in
+terms of the @code{loop} macro. In compiled code, @code{loop} will
+be faster since it generates the loop as in-line code with no
+function calls.
+
address@hidden Sequence Functions, Searching Sequences, Mapping over Sequences,
Sequences
address@hidden Sequence Functions
+
address@hidden
+This section describes a number of Common Lisp functions for
+operating on sequences.
+
address@hidden subseq sequence start &optional end
+This function returns a given subsequence of the argument
address@hidden, which may be a list, string, or vector.
+The indices @var{start} and @var{end} must be in range, and
address@hidden must be no greater than @var{end}. If @var{end}
+is omitted, it defaults to the length of the sequence. The
+return value is always a copy; it does not share structure
+with @var{sequence}.
+
+As an extension to Common Lisp, @var{start} and/or @var{end}
+may be negative, in which case they represent a distance back
+from the end of the sequence. This is for compatibility with
+Emacs' @code{substring} function. Note that @code{subseq} is
+the @emph{only} sequence function that allows negative
address@hidden and @var{end}.
+
+You can use @code{setf} on a @code{subseq} form to replace a
+specified range of elements with elements from another sequence.
+The replacement is done as if by @code{replace}, described below.
address@hidden defun
+
address@hidden concatenate result-type &rest seqs
+This function concatenates the argument sequences together to
+form a result sequence of type @var{result-type}, one of the
+symbols @code{vector}, @code{string}, or @code{list}. The
+arguments are always copied, even in cases such as
address@hidden(concatenate 'list '(1 2 3))} where the result is
+identical to an argument.
address@hidden defun
+
address@hidden fill seq item @t{&key :start :end}
+This function fills the elements of the sequence (or the specified
+part of the sequence) with the value @var{item}.
address@hidden defun
+
address@hidden replace seq1 seq2 @t{&key :start1 :end1 :start2 :end2}
+This function copies part of @var{seq2} into part of @var{seq1}.
+The sequence @var{seq1} is not stretched or resized; the amount
+of data copied is simply the shorter of the source and destination
+(sub)sequences. The function returns @var{seq1}.
+
+If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
+will work correctly even if the regions indicated by the start
+and end arguments overlap. However, if @var{seq1} and @var{seq2}
+are lists which share storage but are not @code{eq}, and the
+start and end arguments specify overlapping regions, the effect
+is undefined.
address@hidden defun
+
address@hidden remove* item seq @t{&key :test :test-not :key :count :start :end
:from-end}
+This returns a copy of @var{seq} with all elements matching
address@hidden removed. The result may share storage with or be
address@hidden to @var{seq} in some circumstances, but the original
address@hidden will not be modified. The @code{:test}, @code{:test-not},
+and @code{:key} arguments define the matching test that is used;
+by default, elements @code{eql} to @var{item} are removed. The
address@hidden:count} argument specifies the maximum number of matching
+elements that can be removed (only the leftmost @var{count} matches
+are removed). The @code{:start} and @code{:end} arguments specify
+a region in @var{seq} in which elements will be removed; elements
+outside that region are not matched or removed. The @code{:from-end}
+argument, if true, says that elements should be deleted from the
+end of the sequence rather than the beginning (this matters only
+if @var{count} was also specified).
address@hidden defun
+
address@hidden delete* item seq @t{&key :test :test-not :key :count :start :end
:from-end}
+This deletes all elements of @var{seq} which match @var{item}.
+It is a destructive operation. Since Emacs Lisp does not support
+stretchable strings or vectors, this is the same as @code{remove*}
+for those sequence types. On lists, @code{remove*} will copy the
+list if necessary to preserve the original list, whereas
address@hidden will splice out parts of the argument list.
+Compare @code{append} and @code{nconc}, which are analogous
+non-destructive and destructive list operations in Emacs Lisp.
address@hidden defun
+
address@hidden remove-if
address@hidden remove-if-not
address@hidden delete-if
address@hidden delete-if-not
+The predicate-oriented functions @code{remove-if}, @code{remove-if-not},
address@hidden, and @code{delete-if-not} are defined similarly.
+
address@hidden remove-duplicates seq @t{&key :test :test-not :key :start :end
:from-end}
+This function returns a copy of @var{seq} with duplicate elements
+removed. Specifically, if two elements from the sequence match
+according to the @code{:test}, @code{:test-not}, and @code{:key}
+arguments, only the rightmost one is retained. If @code{:from-end}
+is true, the leftmost one is retained instead. If @code{:start} or
address@hidden:end} is specified, only elements within that subsequence are
+examined or removed.
address@hidden defun
+
address@hidden delete-duplicates seq @t{&key :test :test-not :key :start :end
:from-end}
+This function deletes duplicate elements from @var{seq}. It is
+a destructive version of @code{remove-duplicates}.
address@hidden defun
+
address@hidden substitute new old seq @t{&key :test :test-not :key :count
:start :end :from-end}
+This function returns a copy of @var{seq}, with all elements
+matching @var{old} replaced with @var{new}. The @code{:count},
address@hidden:start}, @code{:end}, and @code{:from-end} arguments may be
+used to limit the number of substitutions made.
address@hidden defun
+
address@hidden nsubstitute new old seq @t{&key :test :test-not :key :count
:start :end :from-end}
+This is a destructive version of @code{substitute}; it performs
+the substitution using @code{setcar} or @code{aset} rather than
+by returning a changed copy of the sequence.
address@hidden defun
+
address@hidden substitute-if
address@hidden substitute-if-not
address@hidden nsubstitute-if
address@hidden nsubstitute-if-not
+The @code{substitute-if}, @code{substitute-if-not}, @code{nsubstitute-if},
+and @code{nsubstitute-if-not} functions are defined similarly. For
+these, a @var{predicate} is given in place of the @var{old} argument.
+
address@hidden Searching Sequences, Sorting Sequences, Sequence Functions,
Sequences
address@hidden Searching Sequences
+
address@hidden
+These functions search for elements or subsequences in a sequence.
+(See also @code{member*} and @code{assoc*}; @pxref{Lists}.)
+
address@hidden find item seq @t{&key :test :test-not :key :start :end :from-end}
+This function searches @var{seq} for an element matching @var{item}.
+If it finds a match, it returns the matching element. Otherwise,
+it returns @code{nil}. It returns the leftmost match, unless
address@hidden:from-end} is true, in which case it returns the rightmost
+match. The @code{:start} and @code{:end} arguments may be used to
+limit the range of elements that are searched.
address@hidden defun
+
address@hidden position item seq @t{&key :test :test-not :key :start :end
:from-end}
+This function is like @code{find}, except that it returns the
+integer position in the sequence of the matching item rather than
+the item itself. The position is relative to the start of the
+sequence as a whole, even if @code{:start} is non-zero. The function
+returns @code{nil} if no matching element was found.
address@hidden defun
+
address@hidden count item seq @t{&key :test :test-not :key :start :end}
+This function returns the number of elements of @var{seq} which
+match @var{item}. The result is always a nonnegative integer.
address@hidden defun
+
address@hidden find-if
address@hidden find-if-not
address@hidden position-if
address@hidden position-if-not
address@hidden count-if
address@hidden count-if-not
+The @code{find-if}, @code{find-if-not}, @code{position-if},
address@hidden, @code{count-if}, and @code{count-if-not}
+functions are defined similarly.
+
address@hidden mismatch seq1 seq2 @t{&key :test :test-not :key :start1 :end1
:start2 :end2 :from-end}
+This function compares the specified parts of @var{seq1} and
address@hidden If they are the same length and the corresponding
+elements match (according to @code{:test}, @code{:test-not},
+and @code{:key}), the function returns @code{nil}. If there is
+a mismatch, the function returns the index (relative to @var{seq1})
+of the first mismatching element. This will be the leftmost pair of
+elements which do not match, or the position at which the shorter of
+the two otherwise-matching sequences runs out.
+
+If @code{:from-end} is true, then the elements are compared from right
+to left starting at @code{(1- @var{end1})} and @code{(1- @var{end2})}.
+If the sequences differ, then one plus the index of the rightmost
+difference (relative to @var{seq1}) is returned.
+
+An interesting example is @code{(mismatch str1 str2 :key 'upcase)},
+which compares two strings case-insensitively.
address@hidden defun
+
address@hidden search seq1 seq2 @t{&key :test :test-not :key :from-end :start1
:end1 :start2 :end2}
+This function searches @var{seq2} for a subsequence that matches
address@hidden (or part of it specified by @code{:start1} and
address@hidden:end1}.) Only matches which fall entirely within the region
+defined by @code{:start2} and @code{:end2} will be considered.
+The return value is the index of the leftmost element of the
+leftmost match, relative to the start of @var{seq2}, or @code{nil}
+if no matches were found. If @code{:from-end} is true, the
+function finds the @emph{rightmost} matching subsequence.
address@hidden defun
+
address@hidden Sorting Sequences, , Searching Sequences, Sequences
address@hidden Sorting Sequences
+
address@hidden sort* seq predicate @t{&key :key}
+This function sorts @var{seq} into increasing order as determined
+by using @var{predicate} to compare pairs of elements. @var{predicate}
+should return true (address@hidden) if and only if its first argument
+is less than (not equal to) its second argument. For example,
address@hidden<} and @code{string-lessp} are suitable predicate functions
+for sorting numbers and strings, respectively; @code{>} would sort
+numbers into decreasing rather than increasing order.
+
+This function differs from Emacs' built-in @code{sort} in that it
+can operate on any type of sequence, not just lists. Also, it
+accepts a @code{:key} argument which is used to preprocess data
+fed to the @var{predicate} function. For example,
+
address@hidden
+(setq data (sort* data 'string-lessp :key 'downcase))
address@hidden example
+
address@hidden
+sorts @var{data}, a sequence of strings, into increasing alphabetical
+order without regard to case. A @code{:key} function of @code{car}
+would be useful for sorting association lists. It should only be a
+simple accessor though, it's used heavily in the current
+implementation.
+
+The @code{sort*} function is destructive; it sorts lists by actually
+rearranging the @code{cdr} pointers in suitable fashion.
address@hidden defun
+
address@hidden stable-sort seq predicate @t{&key :key}
+This function sorts @var{seq} @dfn{stably}, meaning two elements
+which are equal in terms of @var{predicate} are guaranteed not to
+be rearranged out of their original order by the sort.
+
+In practice, @code{sort*} and @code{stable-sort} are equivalent
+in Emacs Lisp because the underlying @code{sort} function is
+stable by default. However, this package reserves the right to
+use non-stable methods for @code{sort*} in the future.
address@hidden defun
+
address@hidden merge type seq1 seq2 predicate @t{&key :key}
+This function merges two sequences @var{seq1} and @var{seq2} by
+interleaving their elements. The result sequence, of type @var{type}
+(in the sense of @code{concatenate}), has length equal to the sum
+of the lengths of the two input sequences. The sequences may be
+modified destructively. Order of elements within @var{seq1} and
address@hidden is preserved in the interleaving; elements of the two
+sequences are compared by @var{predicate} (in the sense of
address@hidden) and the lesser element goes first in the result.
+When elements are equal, those from @var{seq1} precede those from
address@hidden in the result. Thus, if @var{seq1} and @var{seq2} are
+both sorted according to @var{predicate}, then the result will be
+a merged sequence which is (stably) sorted according to
address@hidden
address@hidden defun
+
address@hidden Lists, Structures, Sequences, Top
address@hidden Lists
+
address@hidden
+The functions described here operate on lists.
+
address@hidden
+* List Functions:: `caddr', `first', `list*', etc.
+* Substitution of Expressions:: `subst', `sublis', etc.
+* Lists as Sets:: `member*', `adjoin', `union', etc.
+* Association Lists:: `assoc*', `rassoc*', `acons', `pairlis'
address@hidden menu
+
address@hidden List Functions, Substitution of Expressions, Lists, Lists
address@hidden List Functions
+
address@hidden
+This section describes a number of simple operations on lists,
+i.e., chains of cons cells.
+
address@hidden caddr x
+This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
+Likewise, this package defines all 28 @address@hidden functions
+where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
+All of these functions are @code{setf}-able, and calls to them
+are expanded inline by the byte-compiler for maximum efficiency.
address@hidden defun
+
address@hidden first x
+This function is a synonym for @code{(car @var{x})}. Likewise,
+the functions @code{second}, @code{third}, @dots{}, through
address@hidden return the given element of the list @var{x}.
address@hidden defun
+
address@hidden rest x
+This function is a synonym for @code{(cdr @var{x})}.
address@hidden defun
+
address@hidden endp x
+Common Lisp defines this function to act like @code{null}, but
+signaling an error if @code{x} is neither a @code{nil} nor a
+cons cell. This package simply defines @code{endp} as a synonym
+for @code{null}.
address@hidden defun
+
address@hidden list-length x
+This function returns the length of list @var{x}, exactly like
address@hidden(length @var{x})}, except that if @var{x} is a circular
+list (where the cdr-chain forms a loop rather than terminating
+with @code{nil}), this function returns @code{nil}. (The regular
address@hidden function would get stuck if given a circular list.)
address@hidden defun
+
address@hidden list* arg &rest others
+This function constructs a list of its arguments. The final
+argument becomes the @code{cdr} of the last cell constructed.
+Thus, @code{(list* @var{a} @var{b} @var{c})} is equivalent to
address@hidden(cons @var{a} (cons @var{b} @var{c}))}, and
address@hidden(list* @var{a} @var{b} nil)} is equivalent to
address@hidden(list @var{a} @var{b})}.
+
+(Note that this function really is called @code{list*} in Common
+Lisp; it is not a name invented for this package like @code{member*}
+or @code{defun*}.)
address@hidden defun
+
address@hidden ldiff list sublist
+If @var{sublist} is a sublist of @var{list}, i.e., is @code{eq} to
+one of the cons cells of @var{list}, then this function returns
+a copy of the part of @var{list} up to but not including
address@hidden For example, @code{(ldiff x (cddr x))} returns
+the first two elements of the list @code{x}. The result is a
+copy; the original @var{list} is not modified. If @var{sublist}
+is not a sublist of @var{list}, a copy of the entire @var{list}
+is returned.
address@hidden defun
+
address@hidden copy-list list
+This function returns a copy of the list @var{list}. It copies
+dotted lists like @code{(1 2 . 3)} correctly.
address@hidden defun
+
address@hidden copy-tree x &optional vecp
+This function returns a copy of the tree of cons cells @var{x}.
+Unlike @code{copy-sequence} (and its alias @code{copy-list}),
+which copies only along the @code{cdr} direction, this function
+copies (recursively) along both the @code{car} and the @code{cdr}
+directions. If @var{x} is not a cons cell, the function simply
+returns @var{x} unchanged. If the optional @var{vecp} argument
+is true, this function copies vectors (recursively) as well as
+cons cells.
address@hidden defun
+
address@hidden tree-equal x y @t{&key :test :test-not :key}
+This function compares two trees of cons cells. If @var{x} and
address@hidden are both cons cells, their @code{car}s and @code{cdr}s are
+compared recursively. If neither @var{x} nor @var{y} is a cons
+cell, they are compared by @code{eql}, or according to the
+specified test. The @code{:key} function, if specified, is
+applied to the elements of both trees. @xref{Sequences}.
address@hidden defun
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Substitution of Expressions, Lists as Sets, List Functions, Lists
address@hidden Substitution of Expressions
+
address@hidden
+These functions substitute elements throughout a tree of cons
+cells. (@xref{Sequence Functions}, for the @code{substitute}
+function, which works on just the top-level elements of a list.)
+
address@hidden subst new old tree @t{&key :test :test-not :key}
+This function substitutes occurrences of @var{old} with @var{new}
+in @var{tree}, a tree of cons cells. It returns a substituted
+tree, which will be a copy except that it may share storage with
+the argument @var{tree} in parts where no substitutions occurred.
+The original @var{tree} is not modified. This function recurses
+on, and compares against @var{old}, both @code{car}s and @code{cdr}s
+of the component cons cells. If @var{old} is itself a cons cell,
+then matching cells in the tree are substituted as usual without
+recursively substituting in that cell. Comparisons with @var{old}
+are done according to the specified test (@code{eql} by default).
+The @code{:key} function is applied to the elements of the tree
+but not to @var{old}.
address@hidden defun
+
address@hidden nsubst new old tree @t{&key :test :test-not :key}
+This function is like @code{subst}, except that it works by
+destructive modification (by @code{setcar} or @code{setcdr})
+rather than copying.
address@hidden defun
+
address@hidden subst-if
address@hidden subst-if-not
address@hidden nsubst-if
address@hidden nsubst-if-not
+The @code{subst-if}, @code{subst-if-not}, @code{nsubst-if}, and
address@hidden functions are defined similarly.
+
address@hidden sublis alist tree @t{&key :test :test-not :key}
+This function is like @code{subst}, except that it takes an
+association list @var{alist} of @address@hidden pairs.
+Each element of the tree (after applying the @code{:key}
+function, if any), is compared with the @code{car}s of
address@hidden; if it matches, it is replaced by the corresponding
address@hidden
address@hidden defun
+
address@hidden nsublis alist tree @t{&key :test :test-not :key}
+This is a destructive version of @code{sublis}.
address@hidden defun
+
address@hidden Lists as Sets, Association Lists, Substitution of Expressions,
Lists
address@hidden Lists as Sets
+
address@hidden
+These functions perform operations on lists which represent sets
+of elements.
+
address@hidden member* item list @t{&key :test :test-not :key}
+This function searches @var{list} for an element matching @var{item}.
+If a match is found, it returns the cons cell whose @code{car} was
+the matching element. Otherwise, it returns @code{nil}. Elements
+are compared by @code{eql} by default; you can use the @code{:test},
address@hidden:test-not}, and @code{:key} arguments to modify this behavior.
address@hidden
+
+Note that this function's name is suffixed by @samp{*} to avoid
+the incompatible @code{member} function defined in Emacs.
+(That function uses @code{equal} for comparisons; it is equivalent
+to @code{(member* @var{item} @var{list} :test 'equal)}.)
address@hidden defun
+
address@hidden member-if
address@hidden member-if-not
+The @code{member-if} and @code{member-if-not} functions
+analogously search for elements which satisfy a given predicate.
+
address@hidden tailp sublist list
+This function returns @code{t} if @var{sublist} is a sublist of
address@hidden, i.e., if @var{sublist} is @code{eql} to @var{list} or to
+any of its @code{cdr}s.
address@hidden defun
+
address@hidden adjoin item list @t{&key :test :test-not :key}
+This function conses @var{item} onto the front of @var{list},
+like @code{(cons @var{item} @var{list})}, but only if @var{item}
+is not already present on the list (as determined by @code{member*}).
+If a @code{:key} argument is specified, it is applied to
address@hidden as well as to the elements of @var{list} during
+the search, on the reasoning that @var{item} is ``about'' to
+become part of the list.
address@hidden defun
+
address@hidden union list1 list2 @t{&key :test :test-not :key}
+This function combines two lists which represent sets of items,
+returning a list that represents the union of those two sets.
+The result list will contain all items which appear in @var{list1}
+or @var{list2}, and no others. If an item appears in both
address@hidden and @var{list2} it will be copied only once. If
+an item is duplicated in @var{list1} or @var{list2}, it is
+undefined whether or not that duplication will survive in the
+result list. The order of elements in the result list is also
+undefined.
address@hidden defun
+
address@hidden nunion list1 list2 @t{&key :test :test-not :key}
+This is a destructive version of @code{union}; rather than copying,
+it tries to reuse the storage of the argument lists if possible.
address@hidden defun
+
address@hidden intersection list1 list2 @t{&key :test :test-not :key}
+This function computes the intersection of the sets represented
+by @var{list1} and @var{list2}. It returns the list of items
+which appear in both @var{list1} and @var{list2}.
address@hidden defun
+
address@hidden nintersection list1 list2 @t{&key :test :test-not :key}
+This is a destructive version of @code{intersection}. It
+tries to reuse storage of @var{list1} rather than copying.
+It does @emph{not} reuse the storage of @var{list2}.
address@hidden defun
+
address@hidden set-difference list1 list2 @t{&key :test :test-not :key}
+This function computes the ``set difference'' of @var{list1}
+and @var{list2}, i.e., the set of elements that appear in
address@hidden but @emph{not} in @var{list2}.
address@hidden defun
+
address@hidden nset-difference list1 list2 @t{&key :test :test-not :key}
+This is a destructive @code{set-difference}, which will try
+to reuse @var{list1} if possible.
address@hidden defun
+
address@hidden set-exclusive-or list1 list2 @t{&key :test :test-not :key}
+This function computes the ``set exclusive or'' of @var{list1}
+and @var{list2}, i.e., the set of elements that appear in
+exactly one of @var{list1} and @var{list2}.
address@hidden defun
+
address@hidden nset-exclusive-or list1 list2 @t{&key :test :test-not :key}
+This is a destructive @code{set-exclusive-or}, which will try
+to reuse @var{list1} and @var{list2} if possible.
address@hidden defun
+
address@hidden subsetp list1 list2 @t{&key :test :test-not :key}
+This function checks whether @var{list1} represents a subset
+of @var{list2}, i.e., whether every element of @var{list1}
+also appears in @var{list2}.
address@hidden defun
+
address@hidden Association Lists, , Lists as Sets, Lists
address@hidden Association Lists
+
address@hidden
+An @dfn{association list} is a list representing a mapping from
+one set of values to another; any list whose elements are cons
+cells is an association list.
+
address@hidden assoc* item a-list @t{&key :test :test-not :key}
+This function searches the association list @var{a-list} for an
+element whose @code{car} matches (in the sense of @code{:test},
address@hidden:test-not}, and @code{:key}, or by comparison with @code{eql})
+a given @var{item}. It returns the matching element, if any,
+otherwise @code{nil}. It ignores elements of @var{a-list} which
+are not cons cells. (This corresponds to the behavior of
address@hidden and @code{assoc} in Emacs Lisp; Common Lisp's
address@hidden ignores @code{nil}s but considers any other non-cons
+elements of @var{a-list} to be an error.)
address@hidden defun
+
address@hidden rassoc* item a-list @t{&key :test :test-not :key}
+This function searches for an element whose @code{cdr} matches
address@hidden If @var{a-list} represents a mapping, this applies
+the inverse of the mapping to @var{item}.
address@hidden defun
+
address@hidden assoc-if
address@hidden assoc-if-not
address@hidden rassoc-if
address@hidden rassoc-if-not
+The @code{assoc-if}, @code{assoc-if-not}, @code{rassoc-if},
+and @code{rassoc-if-not} functions are defined similarly.
+
+Two simple functions for constructing association lists are:
+
address@hidden acons key value alist
+This is equivalent to @code{(cons (cons @var{key} @var{value}) @var{alist})}.
address@hidden defun
+
address@hidden pairlis keys values &optional alist
+This is equivalent to @code{(nconc (mapcar* 'cons @var{keys} @var{values})
address@hidden)}.
address@hidden defun
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Structures, Assertions, Lists, Top
address@hidden Structures
+
address@hidden
+The Common Lisp @dfn{structure} mechanism provides a general way
+to define data types similar to C's @code{struct} types. A
+structure is a Lisp object containing some number of @dfn{slots},
+each of which can hold any Lisp data object. Functions are
+provided for accessing and setting the slots, creating or copying
+structure objects, and recognizing objects of a particular structure
+type.
+
+In true Common Lisp, each structure type is a new type distinct
+from all existing Lisp types. Since the underlying Emacs Lisp
+system provides no way to create new distinct types, this package
+implements structures as vectors (or lists upon request) with a
+special ``tag'' symbol to identify them.
+
address@hidden defstruct name address@hidden
+The @code{defstruct} form defines a new structure type called
address@hidden, with the specified @var{slots}. (The @var{slots}
+may begin with a string which documents the structure type.)
+In the simplest case, @var{name} and each of the @var{slots}
+are symbols. For example,
+
address@hidden
+(defstruct person name age sex)
address@hidden example
+
address@hidden
+defines a struct type called @code{person} which contains three
+slots. Given a @code{person} object @var{p}, you can access those
+slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
+and @code{(person-sex @var{p})}. You can also change these slots by
+using @code{setf} on any of these place forms:
+
address@hidden
+(incf (person-age birthday-boy))
address@hidden example
+
+You can create a new @code{person} by calling @code{make-person},
+which takes keyword arguments @code{:name}, @code{:age}, and
address@hidden:sex} to specify the initial values of these slots in the
+new object. (Omitting any of these arguments leaves the corresponding
+slot ``undefined,'' according to the Common Lisp standard; in Emacs
+Lisp, such uninitialized slots are filled with @code{nil}.)
+
+Given a @code{person}, @code{(copy-person @var{p})} makes a new
+object of the same type whose slots are @code{eq} to those of @var{p}.
+
+Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
+true if @var{x} looks like a @code{person}, false otherwise. (Again,
+in Common Lisp this predicate would be exact; in Emacs Lisp the
+best it can do is verify that @var{x} is a vector of the correct
+length which starts with the correct tag symbol.)
+
+Accessors like @code{person-name} normally check their arguments
+(effectively using @code{person-p}) and signal an error if the
+argument is the wrong type. This check is affected by
address@hidden(optimize (safety @dots{}))} declarations. Safety level 1,
+the default, uses a somewhat optimized check that will detect all
+incorrect arguments, but may use an uninformative error message
+(e.g., ``expected a vector'' instead of ``expected a @code{person}'').
+Safety level 0 omits all checks except as provided by the underlying
address@hidden call; safety levels 2 and 3 do rigorous checking that will
+always print a descriptive error message for incorrect inputs.
address@hidden
+
address@hidden
+(setq dave (make-person :name "Dave" :sex 'male))
+ @result{} [cl-struct-person "Dave" nil male]
+(setq other (copy-person dave))
+ @result{} [cl-struct-person "Dave" nil male]
+(eq dave other)
+ @result{} nil
+(eq (person-name dave) (person-name other))
+ @result{} t
+(person-p dave)
+ @result{} t
+(person-p [1 2 3 4])
+ @result{} nil
+(person-p "Bogus")
+ @result{} nil
+(person-p '[cl-struct-person counterfeit person object])
+ @result{} t
address@hidden example
+
+In general, @var{name} is either a name symbol or a list of a name
+symbol followed by any number of @dfn{struct options}; each @var{slot}
+is either a slot symbol or a list of the form @samp{(@var{slot-name}
address@hidden @address@hidden)}. The @var{default-value}
+is a Lisp form which is evaluated any time an instance of the
+structure type is created without specifying that slot's value.
+
+Common Lisp defines several slot options, but the only one
+implemented in this package is @code{:read-only}. A address@hidden
+value for this option means the slot should not be @code{setf}-able;
+the slot's value is determined when the object is created and does
+not change afterward.
+
address@hidden
+(defstruct person
+ (name nil :read-only t)
+ age
+ (sex 'unknown))
address@hidden example
+
+Any slot options other than @code{:read-only} are ignored.
+
+For obscure historical reasons, structure options take a different
+form than slot options. A structure option is either a keyword
+symbol, or a list beginning with a keyword symbol possibly followed
+by arguments. (By contrast, slot options are key-value pairs not
+enclosed in lists.)
+
address@hidden
+(defstruct (person (:constructor create-person)
+ (:type list)
+ :named)
+ name age sex)
address@hidden example
+
+The following structure options are recognized.
+
address@hidden @code
address@hidden
address@hidden in
address@hidden@address@hidden
address@hidden iftex
address@hidden :conc-name
+The argument is a symbol whose print name is used as the prefix for
+the names of slot accessor functions. The default is the name of
+the struct type followed by a hyphen. The option @code{(:conc-name p-)}
+would change this prefix to @code{p-}. Specifying @code{nil} as an
+argument means no prefix, so that the slot names themselves are used
+to name the accessor functions.
+
address@hidden :constructor
+In the simple case, this option takes one argument which is an
+alternate name to use for the constructor function. The default
+is @address@hidden, e.g., @code{make-person}. The above
+example changes this to @code{create-person}. Specifying @code{nil}
+as an argument means that no standard constructor should be
+generated at all.
+
+In the full form of this option, the constructor name is followed
+by an arbitrary argument list. @xref{Program Structure}, for a
+description of the format of Common Lisp argument lists. All
+options, such as @code{&rest} and @code{&key}, are supported.
+The argument names should match the slot names; each slot is
+initialized from the corresponding argument. Slots whose names
+do not appear in the argument list are initialized based on the
address@hidden in their slot descriptor. Also, @code{&optional}
+and @code{&key} arguments which don't specify defaults take their
+defaults from the slot descriptor. It is valid to include arguments
+which don't correspond to slot names; these are useful if they are
+referred to in the defaults for optional, keyword, or @code{&aux}
+arguments which @emph{do} correspond to slots.
+
+You can specify any number of full-format @code{:constructor}
+options on a structure. The default constructor is still generated
+as well unless you disable it with a simple-format @code{:constructor}
+option.
+
address@hidden
+(defstruct
+ (person
+ (:constructor nil) ; no default constructor
+ (:constructor new-person (name sex &optional (age 0)))
+ (:constructor new-hound (&key (name "Rover")
+ (dog-years 0)
+ &aux (age (* 7 dog-years))
+ (sex 'canine))))
+ name age sex)
address@hidden example
+
+The first constructor here takes its arguments positionally rather
+than by keyword. (In official Common Lisp terminology, constructors
+that work By Order of Arguments instead of by keyword are called
+``BOA constructors.'' No, I'm not making this up.) For example,
address@hidden(new-person "Jane" 'female)} generates a person whose slots
+are @code{"Jane"}, 0, and @code{female}, respectively.
+
+The second constructor takes two keyword arguments, @code{:name},
+which initializes the @code{name} slot and defaults to @code{"Rover"},
+and @code{:dog-years}, which does not itself correspond to a slot
+but which is used to initialize the @code{age} slot. The @code{sex}
+slot is forced to the symbol @code{canine} with no syntax for
+overriding it.
+
address@hidden :copier
+The argument is an alternate name for the copier function for
+this type. The default is @address@hidden @code{nil}
+means not to generate a copier function. (In this implementation,
+all copier functions are simply synonyms for @code{copy-sequence}.)
+
address@hidden :predicate
+The argument is an alternate name for the predicate which recognizes
+objects of this type. The default is @address@hidden @code{nil}
+means not to generate a predicate function. (If the @code{:type}
+option is used without the @code{:named} option, no predicate is
+ever generated.)
+
+In true Common Lisp, @code{typep} is always able to recognize a
+structure object even if @code{:predicate} was used. In this
+package, @code{typep} simply looks for a function called
address@hidden@var{typename}-p}, so it will work for structure types
+only if they used the default predicate name.
+
address@hidden :include
+This option implements a very limited form of C++-style inheritance.
+The argument is the name of another structure type previously
+created with @code{defstruct}. The effect is to cause the new
+structure type to inherit all of the included structure's slots
+(plus, of course, any new slots described by this struct's slot
+descriptors). The new structure is considered a ``specialization''
+of the included one. In fact, the predicate and slot accessors
+for the included type will also accept objects of the new type.
+
+If there are extra arguments to the @code{:include} option after
+the included-structure name, these options are treated as replacement
+slot descriptors for slots in the included structure, possibly with
+modified default values. Borrowing an example from Steele:
+
address@hidden
+(defstruct person name (age 0) sex)
+ @result{} person
+(defstruct (astronaut (:include person (age 45)))
+ helmet-size
+ (favorite-beverage 'tang))
+ @result{} astronaut
+
+(setq joe (make-person :name "Joe"))
+ @result{} [cl-struct-person "Joe" 0 nil]
+(setq buzz (make-astronaut :name "Buzz"))
+ @result{} [cl-struct-astronaut "Buzz" 45 nil nil tang]
+
+(list (person-p joe) (person-p buzz))
+ @result{} (t t)
+(list (astronaut-p joe) (astronaut-p buzz))
+ @result{} (nil t)
+
+(person-name buzz)
+ @result{} "Buzz"
+(astronaut-name joe)
+ @result{} error: "astronaut-name accessing a non-astronaut"
address@hidden example
+
+Thus, if @code{astronaut} is a specialization of @code{person},
+then every @code{astronaut} is also a @code{person} (but not the
+other way around). Every @code{astronaut} includes all the slots
+of a @code{person}, plus extra slots that are specific to
+astronauts. Operations that work on people (like @code{person-name})
+work on astronauts just like other people.
+
address@hidden :print-function
+In full Common Lisp, this option allows you to specify a function
+which is called to print an instance of the structure type. The
+Emacs Lisp system offers no hooks into the Lisp printer which would
+allow for such a feature, so this package simply ignores
address@hidden:print-function}.
+
address@hidden :type
+The argument should be one of the symbols @code{vector} or @code{list}.
+This tells which underlying Lisp data type should be used to implement
+the new structure type. Vectors are used by default, but
address@hidden(:type list)} will cause structure objects to be stored as
+lists instead.
+
+The vector representation for structure objects has the advantage
+that all structure slots can be accessed quickly, although creating
+vectors is a bit slower in Emacs Lisp. Lists are easier to create,
+but take a relatively long time accessing the later slots.
+
address@hidden :named
+This option, which takes no arguments, causes a characteristic ``tag''
+symbol to be stored at the front of the structure object. Using
address@hidden:type} without also using @code{:named} will result in a
+structure type stored as plain vectors or lists with no identifying
+features.
+
+The default, if you don't specify @code{:type} explicitly, is to
+use named vectors. Therefore, @code{:named} is only useful in
+conjunction with @code{:type}.
+
address@hidden
+(defstruct (person1) name age sex)
+(defstruct (person2 (:type list) :named) name age sex)
+(defstruct (person3 (:type list)) name age sex)
+
+(setq p1 (make-person1))
+ @result{} [cl-struct-person1 nil nil nil]
+(setq p2 (make-person2))
+ @result{} (person2 nil nil nil)
+(setq p3 (make-person3))
+ @result{} (nil nil nil)
+
+(person1-p p1)
+ @result{} t
+(person2-p p2)
+ @result{} t
+(person3-p p3)
+ @result{} error: function person3-p undefined
address@hidden example
+
+Since unnamed structures don't have tags, @code{defstruct} is not
+able to make a useful predicate for recognizing them. Also,
+accessors like @code{person3-name} will be generated but they
+will not be able to do any type checking. The @code{person3-name}
+function, for example, will simply be a synonym for @code{car} in
+this case. By contrast, @code{person2-name} is able to verify
+that its argument is indeed a @code{person2} object before
+proceeding.
+
address@hidden :initial-offset
+The argument must be a nonnegative integer. It specifies a
+number of slots to be left ``empty'' at the front of the
+structure. If the structure is named, the tag appears at the
+specified position in the list or vector; otherwise, the first
+slot appears at that position. Earlier positions are filled
+with @code{nil} by the constructors and ignored otherwise. If
+the type @code{:include}s another type, then @code{:initial-offset}
+specifies a number of slots to be skipped between the last slot
+of the included type and the first new slot.
address@hidden table
address@hidden defspec
+
+Except as noted, the @code{defstruct} facility of this package is
+entirely compatible with that of Common Lisp.
+
address@hidden
address@hidden
address@hidden iftex
+
address@hidden Assertions, Efficiency Concerns, Structures, Top
address@hidden Assertions and Errors
+
address@hidden
+This section describes two macros that test @dfn{assertions}, i.e.,
+conditions which must be true if the program is operating correctly.
+Assertions never add to the behavior of a Lisp program; they simply
+make ``sanity checks'' to make sure everything is as it should be.
+
+If the optimization property @code{speed} has been set to 3, and
address@hidden is less than 3, then the byte-compiler will optimize
+away the following assertions. Because assertions might be optimized
+away, it is a bad idea for them to include side-effects.
+
address@hidden assert test-form [show-args string address@hidden
+This form verifies that @var{test-form} is true (i.e., evaluates to
+a address@hidden value). If so, it returns @code{nil}. If the test
+is not satisfied, @code{assert} signals an error.
+
+A default error message will be supplied which includes @var{test-form}.
+You can specify a different error message by including a @var{string}
+argument plus optional extra arguments. Those arguments are simply
+passed to @code{error} to signal the error.
+
+If the optional second argument @var{show-args} is @code{t} instead
+of @code{nil}, then the error message (with or without @var{string})
+will also include all non-constant arguments of the top-level
address@hidden For example:
+
address@hidden
+(assert (> x 10) t "x is too small: %d")
address@hidden example
+
+This usage of @var{show-args} is an extension to Common Lisp. In
+true Common Lisp, the second argument gives a list of @var{places}
+which can be @code{setf}'d by the user before continuing from the
+error. Since Emacs Lisp does not support continuable errors, it
+makes no sense to specify @var{places}.
address@hidden defspec
+
address@hidden check-type form type [string]
+This form verifies that @var{form} evaluates to a value of type
address@hidden If so, it returns @code{nil}. If not, @code{check-type}
+signals a @code{wrong-type-argument} error. The default error message
+lists the erroneous value along with @var{type} and @var{form}
+themselves. If @var{string} is specified, it is included in the
+error message in place of @var{type}. For example:
+
address@hidden
+(check-type x (integer 1 *) "a positive integer")
address@hidden example
+
address@hidden Predicates}, for a description of the type specifiers
+that may be used for @var{type}.
+
+Note that in Common Lisp, the first argument to @code{check-type}
+must be a @var{place} suitable for use by @code{setf}, because
address@hidden signals a continuable error that allows the
+user to modify @var{place}.
address@hidden defspec
+
+The following error-related macro is also defined:
+
address@hidden ignore-errors address@hidden
+This executes @var{forms} exactly like a @code{progn}, except that
+errors are ignored during the @var{forms}. More precisely, if
+an error is signaled then @code{ignore-errors} immediately
+aborts execution of the @var{forms} and returns @code{nil}.
+If the @var{forms} complete successfully, @code{ignore-errors}
+returns the result of the last @var{form}.
address@hidden defspec
+
address@hidden Efficiency Concerns, Common Lisp Compatibility, Assertions, Top
address@hidden Efficiency Concerns
+
address@hidden Macros
+
address@hidden
+Many of the advanced features of this package, such as @code{defun*},
address@hidden, and @code{setf}, are implemented as Lisp macros. In
+byte-compiled code, these complex notations will be expanded into
+equivalent Lisp code which is simple and efficient. For example,
+the forms
+
address@hidden
+(incf i n)
+(push x (car p))
address@hidden example
+
address@hidden
+are expanded at compile-time to the Lisp forms
+
address@hidden
+(setq i (+ i n))
+(setcar p (cons x (car p)))
address@hidden example
+
address@hidden
+which are the most efficient ways of doing these respective operations
+in Lisp. Thus, there is no performance penalty for using the more
+readable @code{incf} and @code{push} forms in your compiled code.
+
address@hidden code, on the other hand, must expand these macros
+every time they are executed. For this reason it is strongly
+recommended that code making heavy use of macros be compiled.
+(The features labeled ``Special Form'' instead of ``Function'' in
+this manual are macros.) A loop using @code{incf} a hundred times
+will execute considerably faster if compiled, and will also
+garbage-collect less because the macro expansion will not have
+to be generated, used, and thrown away a hundred times.
+
+You can find out how a macro expands by using the
address@hidden function.
+
address@hidden cl-prettyexpand form &optional full
+This function takes a single Lisp form as an argument and inserts
+a nicely formatted copy of it in the current buffer (which must be
+in Lisp mode so that indentation works properly). It also expands
+all Lisp macros which appear in the form. The easiest way to use
+this function is to go to the @code{*scratch*} buffer and type, say,
+
address@hidden
+(cl-prettyexpand '(loop for x below 10 collect x))
address@hidden example
+
address@hidden
+and type @kbd{C-x C-e} immediately after the closing parenthesis;
+the expansion
+
address@hidden
+(block nil
+ (let* ((x 0)
+ (G1004 nil))
+ (while (< x 10)
+ (setq G1004 (cons x G1004))
+ (setq x (+ x 1)))
+ (nreverse G1004)))
address@hidden example
+
address@hidden
+will be inserted into the buffer. (The @code{block} macro is
+expanded differently in the interpreter and compiler, so
address@hidden just leaves it alone. The temporary
+variable @code{G1004} was created by @code{gensym}.)
+
+If the optional argument @var{full} is true, then @emph{all}
+macros are expanded, including @code{block}, @code{eval-when},
+and compiler macros. Expansion is done as if @var{form} were
+a top-level form in a file being compiled. For example,
+
address@hidden
+(cl-prettyexpand '(pushnew 'x list))
+ @print{} (setq list (adjoin 'x list))
+(cl-prettyexpand '(pushnew 'x list) t)
+ @print{} (setq list (if (memq 'x list) list (cons 'x list)))
+(cl-prettyexpand '(caddr (member* 'a list)) t)
+ @print{} (car (cdr (cdr (memq 'a list))))
address@hidden example
+
+Note that @code{adjoin}, @code{caddr}, and @code{member*} all
+have built-in compiler macros to optimize them in common cases.
address@hidden defun
+
address@hidden
address@hidden
+
address@hidden example
address@hidden ifinfo
address@hidden Error Checking
+
address@hidden
+Common Lisp compliance has in general not been sacrificed for the
+sake of efficiency. A few exceptions have been made for cases
+where substantial gains were possible at the expense of marginal
+incompatibility.
+
+The Common Lisp standard (as embodied in Steele's book) uses the
+phrase ``it is an error if'' to indicate a situation which is not
+supposed to arise in complying programs; implementations are strongly
+encouraged but not required to signal an error in these situations.
+This package sometimes omits such error checking in the interest of
+compactness and efficiency. For example, @code{do} variable
+specifiers are supposed to be lists of one, two, or three forms;
+extra forms are ignored by this package rather than signaling a
+syntax error. The @code{endp} function is simply a synonym for
address@hidden in this package. Functions taking keyword arguments
+will accept an odd number of arguments, treating the trailing
+keyword as if it were followed by the value @code{nil}.
+
+Argument lists (as processed by @code{defun*} and friends)
address@hidden checked rigorously except for the minor point just
+mentioned; in particular, keyword arguments are checked for
+validity, and @code{&allow-other-keys} and @code{:allow-other-keys}
+are fully implemented. Keyword validity checking is slightly
+time consuming (though not too bad in byte-compiled code);
+you can use @code{&allow-other-keys} to omit this check. Functions
+defined in this package such as @code{find} and @code{member*}
+do check their keyword arguments for validity.
+
address@hidden
address@hidden
+
address@hidden example
address@hidden ifinfo
address@hidden Optimizing Compiler
+
address@hidden
+Use of the optimizing Emacs compiler is highly recommended; many of the Common
+Lisp macros emit
+code which can be improved by optimization. In particular,
address@hidden (whether explicit or implicit in constructs like
address@hidden and @code{loop}) carry a fair run-time penalty; the
+optimizing compiler removes @code{block}s which are not actually
+referenced by @code{return} or @code{return-from} inside the block.
+
address@hidden Common Lisp Compatibility, Old CL Compatibility, Efficiency
Concerns, Top
address@hidden Common Lisp Compatibility
+
address@hidden
+Following is a list of all known incompatibilities between this
+package and Common Lisp as documented in Steele (2nd edition).
+
+Certain function names, such as @code{member}, @code{assoc}, and
address@hidden, were already taken by (incompatible) Emacs Lisp
+functions; this package appends @samp{*} to the names of its
+Common Lisp versions of these functions.
+
+The word @code{defun*} is required instead of @code{defun} in order
+to use extended Common Lisp argument lists in a function. Likewise,
address@hidden and @code{function*} are versions of those forms
+which understand full-featured argument lists. The @code{&whole}
+keyword does not work in @code{defmacro} argument lists (except
+inside recursive argument lists).
+
+The @code{eql} and @code{equal} predicates do not distinguish
+between IEEE floating-point plus and minus zero. The @code{equalp}
+predicate has several differences with Common Lisp; @pxref{Predicates}.
+
+The @code{setf} mechanism is entirely compatible, except that
+setf-methods return a list of five values rather than five
+values directly. Also, the new address@hidden function'' concept
+(typified by @code{(defun (setf foo) @dots{})}) is not implemented.
+
+The @code{do-all-symbols} form is the same as @code{do-symbols}
+with no @var{obarray} argument. In Common Lisp, this form would
+iterate over all symbols in all packages. Since Emacs obarrays
+are not a first-class package mechanism, there is no way for
address@hidden to locate any but the default obarray.
+
+The @code{loop} macro is complete except that @code{loop-finish}
+and type specifiers are unimplemented.
+
+The multiple-value return facility treats lists as multiple
+values, since Emacs Lisp cannot support multiple return values
+directly. The macros will be compatible with Common Lisp if
address@hidden or @code{values-list} is always used to return to
+a @code{multiple-value-bind} or other multiple-value receiver;
+if @code{values} is used without @address@hidden
+or vice-versa the effect will be different from Common Lisp.
+
+Many Common Lisp declarations are ignored, and others match
+the Common Lisp standard in concept but not in detail. For
+example, local @code{special} declarations, which are purely
+advisory in Emacs Lisp, do not rigorously obey the scoping rules
+set down in Steele's book.
+
+The variable @code{*gensym-counter*} starts out with a pseudo-random
+value rather than with zero. This is to cope with the fact that
+generated symbols become interned when they are written to and
+loaded back from a file.
+
+The @code{defstruct} facility is compatible, except that structures
+are of type @code{:type vector :named} by default rather than some
+special, distinct type. Also, the @code{:type} slot option is ignored.
+
+The second argument of @code{check-type} is treated differently.
+
address@hidden Old CL Compatibility, Porting Common Lisp, Common Lisp
Compatibility, Top
address@hidden Old CL Compatibility
+
address@hidden
+Following is a list of all known incompatibilities between this package
+and the older Quiroz @file{cl.el} package.
+
+This package's emulation of multiple return values in functions is
+incompatible with that of the older package. That package attempted
+to come as close as possible to true Common Lisp multiple return
+values; unfortunately, it could not be 100% reliable and so was prone
+to occasional surprises if used freely. This package uses a simpler
+method, namely replacing multiple values with lists of values, which
+is more predictable though more noticeably different from Common Lisp.
+
+The @code{defkeyword} form and @code{keywordp} function are not
+implemented in this package.
+
+The @code{member}, @code{floor}, @code{ceiling}, @code{truncate},
address@hidden, @code{mod}, and @code{rem} functions are suffixed
+by @samp{*} in this package to avoid collision with existing
+functions in Emacs. The older package simply
+redefined these functions, overwriting the built-in meanings and
+causing serious portability problems. (Some more
+recent versions of the Quiroz package changed the names to
address@hidden, etc.; this package defines the latter names as
+aliases for @code{member*}, etc.)
+
+Certain functions in the old package which were buggy or inconsistent
+with the Common Lisp standard are incompatible with the conforming
+versions in this package. For example, @code{eql} and @code{member}
+were synonyms for @code{eq} and @code{memq} in that package, @code{setf}
+failed to preserve correct order of evaluation of its arguments, etc.
+
+Finally, unlike the older package, this package is careful to
+prefix all of its internal names with @code{cl-}. Except for a
+few functions which are explicitly defined as additional features
+(such as @code{floatp-safe} and @code{letf}), this package does not
+export any address@hidden symbols which are not also part of Common
+Lisp.
+
address@hidden
address@hidden
+
address@hidden example
address@hidden ifinfo
address@hidden The @code{cl-compat} package
+
address@hidden
+The @dfn{CL} package includes emulations of some features of the
+old @file{cl.el}, in the form of a compatibility package
address@hidden To use it, put @code{(require 'cl-compat)} in
+your program.
+
+The old package defined a number of internal routines without
address@hidden prefixes or other annotations. Call to these routines
+may have crept into existing Lisp code. @code{cl-compat}
+provides emulations of the following internal routines:
address@hidden, @code{zip-lists}, @code{unzip-lists},
address@hidden, @code{duplicate-symbols-p},
address@hidden
+
+Some @code{setf} forms translated into calls to internal
+functions that user code might call directly. The functions
address@hidden, @code{setnthcdr}, and @code{setelt} fall in
+this category; they are defined by @code{cl-compat}, but the
+best fix is to change to use @code{setf} properly.
+
+The @code{cl-compat} file defines the keyword functions
address@hidden, @code{keyword-of}, and @code{defkeyword},
+which are not defined by the new @dfn{CL} package because the
+use of keywords as data is discouraged.
+
+The @code{build-klist} mechanism for parsing keyword arguments
+is emulated by @code{cl-compat}; the @code{with-keyword-args}
+macro is not, however, and in any case it's best to change to
+use the more natural keyword argument processing offered by
address@hidden
+
+Multiple return values are treated differently by the two
+Common Lisp packages. The old package's method was more
+compatible with true Common Lisp, though it used heuristics
+that caused it to report spurious multiple return values in
+certain cases. The @code{cl-compat} package defines a set
+of multiple-value macros that are compatible with the old
+CL package; again, they are heuristic in nature, but they
+are guaranteed to work in any case where the old package's
+macros worked. To avoid name collision with the ``official''
+multiple-value facilities, the ones in @code{cl-compat} have
+capitalized names: @code{Values}, @code{Values-list},
address@hidden, etc.
+
+The functions @code{cl-floor}, @code{cl-ceiling}, @code{cl-truncate},
+and @code{cl-round} are defined by @code{cl-compat} to use the
+old-style multiple-value mechanism, just as they did in the old
+package. The newer @code{floor*} and friends return their two
+results in a list rather than as multiple values. Note that
+older versions of the old package used the unadorned names
address@hidden, @code{ceiling}, etc.; @code{cl-compat} cannot use
+these names because they conflict with Emacs built-ins.
+
address@hidden Porting Common Lisp, GNU Free Documentation License, Old CL
Compatibility, Top
address@hidden Porting Common Lisp
+
address@hidden
+This package is meant to be used as an extension to Emacs Lisp,
+not as an Emacs implementation of true Common Lisp. Some of the
+remaining differences between Emacs Lisp and Common Lisp make it
+difficult to port large Common Lisp applications to Emacs. For
+one, some of the features in this package are not fully compliant
+with ANSI or Steele; @pxref{Common Lisp Compatibility}. But there
+are also quite a few features that this package does not provide
+at all. Here are some major omissions that you will want to watch out
+for when bringing Common Lisp code into Emacs.
+
address@hidden @bullet
address@hidden
+Case-insensitivity. Symbols in Common Lisp are case-insensitive
+by default. Some programs refer to a function or variable as
address@hidden in one place and @code{Foo} or @code{FOO} in another.
+Emacs Lisp will treat these as three distinct symbols.
+
+Some Common Lisp code is written entirely in upper case. While Emacs
+is happy to let the program's own functions and variables use
+this convention, calls to Lisp builtins like @code{if} and
address@hidden will have to be changed to lower case.
+
address@hidden
+Lexical scoping. In Common Lisp, function arguments and @code{let}
+bindings apply only to references physically within their bodies
+(or within macro expansions in their bodies). Emacs Lisp, by
+contrast, uses @dfn{dynamic scoping} wherein a binding to a
+variable is visible even inside functions called from the body.
+
+Variables in Common Lisp can be made dynamically scoped by
+declaring them @code{special} or using @code{defvar}. In Emacs
+Lisp it is as if all variables were declared @code{special}.
+
+Often you can use code that was written for lexical scoping
+even in a dynamically scoped Lisp, but not always. Here is
+an example of a Common Lisp code fragment that would fail in
+Emacs Lisp:
+
address@hidden
+(defun map-odd-elements (func list)
+ (loop for x in list
+ for flag = t then (not flag)
+ collect (if flag x (funcall func x))))
+
+(defun add-odd-elements (list x)
+ (map-odd-elements (lambda (a) (+ a x))) list)
address@hidden example
+
address@hidden
+In Common Lisp, the two functions' usages of @code{x} are completely
+independent. In Emacs Lisp, the binding to @code{x} made by
address@hidden will have been hidden by the binding
+in @code{map-odd-elements} by the time the @code{(+ a x)} function
+is called.
+
+(This package avoids such problems in its own mapping functions
+by using names like @code{cl-x} instead of @code{x} internally;
+as long as you don't use the @code{cl-} prefix for your own
+variables no collision can occur.)
+
address@hidden Bindings}, for a description of the @code{lexical-let}
+form which establishes a Common Lisp-style lexical binding, and some
+examples of how it differs from Emacs' regular @code{let}.
+
address@hidden
+Reader macros. Common Lisp includes a second type of macro that
+works at the level of individual characters. For example, Common
+Lisp implements the quote notation by a reader macro called @code{'},
+whereas Emacs Lisp's parser just treats quote as a special case.
+Some Lisp packages use reader macros to create special syntaxes
+for themselves, which the Emacs parser is incapable of reading.
+
+The lack of reader macros, incidentally, is the reason behind
+Emacs Lisp's unusual backquote syntax. Since backquotes are
+implemented as a Lisp package and not built-in to the Emacs
+parser, they are forced to use a regular macro named @code{`}
+which is used with the standard function/macro call notation.
+
address@hidden
+Other syntactic features. Common Lisp provides a number of
+notations beginning with @code{#} that the Emacs Lisp parser
+won't understand. For example, @samp{#| ... |#} is an
+alternate comment notation, and @samp{#+lucid (foo)} tells
+the parser to ignore the @code{(foo)} except in Lucid Common
+Lisp.
+
address@hidden
+Packages. In Common Lisp, symbols are divided into @dfn{packages}.
+Symbols that are Lisp built-ins are typically stored in one package;
+symbols that are vendor extensions are put in another, and each
+application program would have a package for its own symbols.
+Certain symbols are ``exported'' by a package and others are
+internal; certain packages ``use'' or import the exported symbols
+of other packages. To access symbols that would not normally be
+visible due to this importing and exporting, Common Lisp provides
+a syntax like @code{package:symbol} or @code{package::symbol}.
+
+Emacs Lisp has a single namespace for all interned symbols, and
+then uses a naming convention of putting a prefix like @code{cl-}
+in front of the name. Some Emacs packages adopt the Common Lisp-like
+convention of using @code{cl:} or @code{cl::} as the prefix.
+However, the Emacs parser does not understand colons and just
+treats them as part of the symbol name. Thus, while @code{mapcar}
+and @code{lisp:mapcar} may refer to the same symbol in Common
+Lisp, they are totally distinct in Emacs Lisp. Common Lisp
+programs which refer to a symbol by the full name sometimes
+and the short name other times will not port cleanly to Emacs.
+
+Emacs Lisp does have a concept of ``obarrays,'' which are
+package-like collections of symbols, but this feature is not
+strong enough to be used as a true package mechanism.
+
address@hidden
+The @code{format} function is quite different between Common
+Lisp and Emacs Lisp. It takes an additional ``destination''
+argument before the format string. A destination of @code{nil}
+means to format to a string as in Emacs Lisp; a destination
+of @code{t} means to write to the terminal (similar to
address@hidden in Emacs). Also, format control strings are
+utterly different; @code{~} is used instead of @code{%} to
+introduce format codes, and the set of available codes is
+much richer. There are no notations like @code{\n} for
+string literals; instead, @code{format} is used with the
+``newline'' format code, @code{~%}. More advanced formatting
+codes provide such features as paragraph filling, case
+conversion, and even loops and conditionals.
+
+While it would have been possible to implement most of Common
+Lisp @code{format} in this package (under the name @code{format*},
+of course), it was not deemed worthwhile. It would have required
+a huge amount of code to implement even a decent subset of
address@hidden, yet the functionality it would provide over
+Emacs Lisp's @code{format} would rarely be useful.
+
address@hidden
+Vector constants use square brackets in Emacs Lisp, but
address@hidden(a b c)} notation in Common Lisp. To further complicate
+matters, Emacs has its own @code{#(} notation for
+something entirely different---strings with properties.
+
address@hidden
+Characters are distinct from integers in Common Lisp. The
+notation for character constants is also different: @code{#\A}
+instead of @code{?A}. Also, @code{string=} and @code{string-equal}
+are synonyms in Emacs Lisp whereas the latter is case-insensitive
+in Common Lisp.
+
address@hidden
+Data types. Some Common Lisp data types do not exist in Emacs
+Lisp. Rational numbers and complex numbers are not present,
+nor are large integers (all integers are ``fixnums''). All
+arrays are one-dimensional. There are no readtables or pathnames;
+streams are a set of existing data types rather than a new data
+type of their own. Hash tables, random-states, structures, and
+packages (obarrays) are built from Lisp vectors or lists rather
+than being distinct types.
+
address@hidden
+The Common Lisp Object System (CLOS) is not implemented,
+nor is the Common Lisp Condition System. However, the EIEIO package
+from @uref{ftp://ftp.ultranet.com/pub/zappo} does implement some
+CLOS functionality.
+
address@hidden
+Common Lisp features that are completely redundant with Emacs
+Lisp features of a different name generally have not been
+implemented. For example, Common Lisp writes @code{defconstant}
+where Emacs Lisp uses @code{defconst}. Similarly, @code{make-list}
+takes its arguments in different ways in the two Lisps but does
+exactly the same thing, so this package has not bothered to
+implement a Common Lisp-style @code{make-list}.
+
address@hidden
+A few more notable Common Lisp features not included in this
+package: @code{compiler-let}, @code{tagbody}, @code{prog},
address@hidden/dpb}, @code{parse-integer}, @code{cerror}.
+
address@hidden
+Recursion. While recursion works in Emacs Lisp just like it
+does in Common Lisp, various details of the Emacs Lisp system
+and compiler make recursion much less efficient than it is in
+most Lisps. Some schools of thought prefer to use recursion
+in Lisp over other techniques; they would sum a list of
+numbers using something like
+
address@hidden
+(defun sum-list (list)
+ (if list
+ (+ (car list) (sum-list (cdr list)))
+ 0))
address@hidden example
+
address@hidden
+where a more iteratively-minded programmer might write one of
+these forms:
+
address@hidden
+(let ((total 0)) (dolist (x my-list) (incf total x)) total)
+(loop for x in my-list sum x)
address@hidden example
+
+While this would be mainly a stylistic choice in most Common Lisps,
+in Emacs Lisp you should be aware that the iterative forms are
+much faster than recursion. Also, Lisp programmers will want to
+note that the current Emacs Lisp compiler does not optimize tail
+recursion.
address@hidden itemize
+
address@hidden GNU Free Documentation License, Function Index, Porting Common
Lisp, Top
address@hidden GNU Free Documentation License
address@hidden doclicense.texi
+
address@hidden Function Index, Variable Index, GNU Free Documentation License,
Top
address@hidden Function Index
+
address@hidden fn
+
address@hidden Variable Index, , Function Index, Top
address@hidden Variable Index
+
address@hidden vr
+
address@hidden odd
address@hidden
address@hidden
+
address@hidden
+ arch-tag: b61e7200-3bfa-4a70-a9d3-095e152696f8
address@hidden ignore
- [Emacs-diffs] Changes to cl.texi,
Glenn Morris <=